Hi All,
I am starting a new message thread on diagnosing, and hopefully fixing, a gas leak in the engine of my 1973 Penton Hare Scrambler. We exchanged already quite number of useful messages and I thought it would be useful to have this listed under a more appropriate subject line. For the previous messages see:
http://www.pentonusa.org/forum/topic.asp?TOPIC_ID=16030&whichpage=1
As discussed previously I replaced the right hand side crank seal and gasket under the seal holder. I also did another thing: add more soap to my "soapy leak testing fluid". The small leak at the crank is indeed fixed now. However, the leak rate is similar to what I observed before: I get a half life time (time required to loose half the pressure) of about 4.3 minutes. Is there any guidance as to what leakage rate is acceptable? This is certainly not a very large leak but observable. More spraying with soapy water revealed a leak at the cylinder base which is probably responsible for the observed gas loss. If the current leak rate is too large I probably will have to take the cylinder off and the engine out of the frame. I already checked the cylinder head bolts and found them tight. I increased the torque on the Allen head bolts from 20 to 25 foot*pound; no difference. I also checked the case bolts and found them correctly torqued too. Are there any suggestions out there on how to deal with a leak at the cylinder base not requiring engine disassembly?
As usual I appreciate your practical knowledge on all things Penton!
Andreas
P.S.: The leak at the cylinder base appears to be in the middle where the two engine halves meet.
Andreas,
If you pull the jug, try coating the base gasket with a thin coating of grease before the reinstall. Sometimes works wonders!
_____________________________________________________________________________________
"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."
1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax
I was trying to get around taking the cylinder off. I guess this will require removal of the engine from the frame. Do you guys use new foot and head gaskets for every cylinder removal? How long will the grease seal? Will it not simply be blown out when the engine heats up?
Cheers
Andreas
I'm a firm believer in good ol' #2 Permatex. A thin coat on both sides of the base gasket. It's pretty sticky, and doesn't get hard. When assembling the engine, the fit of the two case halves at the cylinder base needs to be checked, especially if you have replaced one side or the other, and appropriate measures taken to even them out. Then, when dry fitting the cylinder to the bottom end, a check of the deck height dimension so you can adjust the base gasket thickness as necessary. Most vintage Japanese bikes, which were mass produced in far greater numbers, generally are pretty consistent. I have heard and read that this area needs watching and attention on KTM and other Euro brand engines. You may not need to remove the engine from the frame, unless you have a significant mis-match in the center cases. Good luck with the rest of the procedure and I'll continue to watch the thread.
Type at you later,
Dan McEntee
Andreas - at this point you have been fighting an engine that is not running properly for months. Pulling the top end can be done in a weekend or less. Make sure you have a second set of hands - KTM cylinders are heavy & hard to seat on the rings by yourself without someone to help steady things.
You can sometimes get away with pulling the studs to get the cylinder off in the frame (double nut them with the head nuts). On some engines you get a little more room by removing the front engine mounts & pivoting the engine downwards.
Dan is correct about setting the deck height. On a KTM engine it wasn't so much about poor castings as it is a typical example of Austrian/German precision. OEM gasket sets came with a variety of different thickness base gaskets to allow you to set the deck height precisely to factory racing specs (blueprinted),
The proper way is to torque the head to initially compress the gaskets, remove the head to confirm the height, add or remove gaskets as necessary, assemble, then run the engine, and check it again.
In reality most engines were just run after torquing once and re-checking - skipping the "run once" step. As a practical manner whenever we tore down a customers engine we would "mic" the existing gaskets (the compressed portion in the middle) to get a starting point. Deck heights were precisely set at the factory and were usually only off if a non-trained mechanic had been in there.
The grease does not seal anything - it simply makes the gasket supple so that it can conform to the jug and cases. Artificial products like permatex are not necessary unless something is scarred or damaged by an errant putty or pocket knife.
Gaskets do not necessarily need to be replaced every time if they are intact. The grease helps with finding a gasket reusable, while the other products sometimes glue the gasket down causing it to tear or stick on dis-assembly.
Last but most importantly - if you go in - make sure that you have the tiny hole in the exhaust port side of the piston for proper lubrication of the exhaust port. If this hasn't been done ask us for instructions.
_____________________________________________________________________________________
"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."
1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax
Hi All,
This is great advice. I will go for that! The gaskets I used were all new. I tried to adjust the deck height but, as you indicated, skipped the middle step. I measured 165 psi compression pressure after assembly and concluded this to be good. The two crank housing halfs are original and not mix and match. I have a second head gasket but purchased only one set of base gaskets. Yes the little lubrication holes (actually two of them along the exhaust port bridge) have been drilled into the piston.
This is actually exactly the kind of advice I was hoping for, thanks for taking time to lay out the details.
Cheers
Andreas
Hi All,
I leak checked all seams of the engine again and the only leak I could identify is the one at the cylinder base were the crank cases meet. I have already taken the exhaust off:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4497_zpsm0iskjsv.jpg)
Tomorrow I'll take the cylinder off to inspect the situation a little closer. I had hoped to avoid this but, I guess, there is no other way. I also got some fiber clutch plates, I'll put these in too along with a new clutch push rod.
Hope you'll continue helping me diagnose the problem(s) on-line, cheers
Andreas
Hi All,
Today I took the cylinder off my 1973 Penton Hare Scrambler. Before that I re-measured the deck height (the cylinder was pulled down by hand-tightening the four studs):
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4515_zpsgfiri8m0.jpg)
I re-set TDC for every measurement and found an average of 0.95 mm after 10 measurements. A little less than the recommended 1.1 to 1.2 mm but not dramatically so. For the next assembly I'll correct this issue. The cylinder head was properly sealed, there is no indication of any blow-by of gas. The gasket was stuck so I'll need a new one.
However, after taking the cylinder off the deeper reason for my troubles became apparent:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4517_zpskvmqrmu1.jpg)
The crank shaft is covered in transmission fluid, there has to be a sizeable leak. I am afraid there is no other choice now but to take the engine out of the frame and split the crank case. The crank will have to come out to get at the left seal and all that good stuff. It seems I am back if not to square one but perhaps two.
Cheers
Andreas
Andreas - when you tear it down pay particular attention to the center case gasket between the crankcase & the gearbox. Its very thin in that area. it's possible that is your problem, not the seal. They seldom want to lie flat.
Get a whole gasket set, not just a seal. When you get ready to reassemble the engine put the new center case gasket in warm water for a couple minutes, then coat both sides of the gasket with a thin layer of grease while it's still wet.
This helps the gasket to lay down and stay where it is supposed to. Get the screws in loosely and keep checking the gasket as you bring the cases back together. Don't forget to put a little oil on the main bearings, and a dab of grease on the inner seal too.
As soaked as your base gaskets are they should be changed. Either mic them for thickness, or put the same combination of thicknesses as you currently have since you already have the deck height where you want it. Grease them lightly too.
Good luck - you'll get it!
_____________________________________________________________________________________
"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."
1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax
Clark, thanks for your advice! I will have a good look at the center gasket after splitting the crank case and then try to assess the problem. I have another center gasket but no set of base gaskets, only those I didn't use the last time around. After splitting the case I should probably replace the left crank seal just to make sure...
Thanks again
Andreas
Hi All,
Unfortunately I had no time to work much on my 1973 Penton Hare Scrambler lately. If you look through this post you'll see the problem I have: my rebuilt engine doesn't work right. After all kinds of things tried out I believe the real problem has been identified: transmission fluid in the crank case. It was pointed out that this could be due to an improperly installed center case gasket. That would be great because it is relatively easy to fix. Last week I took the engine out of the frame again and split the cases. I took photos of the center gasket and the sealing surface:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4551_zpsnhugcljm.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4552_zpsryvjnxfz.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4553_zpsrtdgkbtt.jpg)
I can't see anything wrong with the center gasket or the case surfaces. I am afraid I have to dig even deeper now, remove the crank and replace the left crank seal. At this point I am back to where I was a year ago:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4556_zpsskisvpgv.jpg)
As always your insights and ideas are welcome!
Cheers
Andreas
Just keep plugging away at it Andreas. You may be experiencing the problems but are doing a good job of trying to pin point the problem. The threads have been most informative and instructional with great photos. others should and will learn from this experience.
Good luck the rest of the way,
Dan McEntee
I hate to be the possible bearer of bad news, but on the early black case 250 engines, the right hand center engine cases sometime crack near the right rear cylinder stud area, and where the engine strut attaches. The silver engine cases are much thicker in this area.
In your photo showing the piston, and with the studs removed I see a crack emanating from where the notch for the ignition wires is in the case! Good luck!
Good eye JP, I have a 4" magnifying glass for finding those hairline cracks.
Nice Norton Andreas, what year?
Raymond
Down East Pentons
I'll inspect the crank case with a magnifying glass tonight.
The Norton is a 1973 Commando 850 cm^3. I am owning it since 1987. It has about 20,000 miles and, to the best of my knowledge, the engine has never been opened since assembly at the Norton factory.
I appreciate your feedback, good news bad news: doesn't matter. The only thing that matters is to identify the real problems and solve them!
Andreas
JP you really have a good eye! This weekend I took a photo of the right housing half:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/100_4568_zpswtgwaqz1.jpg)
Indeed, there is a crack starting from the cable recess. However, it does not extend into the crank case and is not the cause for the leakage. Maybe the little rubber grommet is too tight once the cables are in and caused this. I bought a new one and already opened up its interior so it fits into the case opening; but maybe not enough. I will try to fix the crack with JP weld as this doesn't seem structural.
Cheers
Andreas
Hi Penton enthusiasts,
Lately I didn't do much work on my in-parts-again 1973 Penton Hare Scrambler. This post is not strictly Penton but for your enjoyment: I spent time making my 1973 Norton Commando operational again; here a short video of a test ride.
https://www.youtube.com/watch?v=3KopPQnFYts
I'll get back to my Penton now.
Cheers
Andreas
P.S.: Does this thing with not having the key in the ignition and the gloves on only happen to me?
Good luck Andreas, maybe the center case gasket didn't lay flat, or it has shrunk and has moved off the case split area, been there, done that on a Sachs motor once.
I had hoped for that too but, unfortunately, this doesn't seem to be the case. Have a look at an earlier post in this thread. When I split the cases I found the gasket in good order. I posted a photo, it looks ok to me. I am afraid the problem is with the left hand side crank seal, the one that is really hard to replace.
Cheers
Andreas
Hi All,
Today I took my 250 ccm engine further apart to get the leakage problem resolved. I went from this:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4772_zps2epmij5n.jpg)
To disassembled again. I still need to figure out what caused the engine to leak. Have a look at the two images below.
Configuration A:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4796_zpsj6z1cqbv.jpg)
This is how I had the left crank seal installed. Or does it need to go the other way around?
Configuration B:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4795_zpswxsc3c8h.jpg)
This is my question for all KTM engine pros: which way around, A or B, does this seal need to be installed?
I further noted that the seal was sitting in there slightly crooked, perhaps the angular mismatch between sealing lip and crank pin caused the leak. I would greatly appreciate guidance in this matter as I don't want to take this engine apart yet another time!
Thanks in advance!
Andreas
Seal should be installed as in your upper/first photo, open side in toward crankshaft. I would be wary of a seal with a metal outer sleeve, leaks can occur around the seal outer edge. Try to find a seal that has rubber around the outside diameter. Yes, a crooked installation could be problematic.
Also check any areas of the case that have epoxy applied to them from the factory, could be porosity there, epoxy may have dried out and shrunk away from case. Clean, sand, reapply new epoxy if needed.
Andreas,
When you initially rebuilt this, did you replace the O-ring under the aluminum spacer?
Thanks,
Kevin
Kevin, yes I did. All seals, gaskets, and bearings have been replaced. The cylinder has been bored, a new piston installed, it has a new connecting rod too. There is nothing old in there.
Andreas
Hi Penton Owners Group,
If you follow this post you might remember that a POGer with a sharp eye discovered a crack in the right crank housing half of my 1973 Hare Scrambler. Closer inspection actually showed this to be really the case:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4816_zps9mgnr9c1.jpg)
This crack originates from the little cutout for the cables. I believe that the deeper problem is that the rubber grommet that fixes the cable is too tight (I noted this and despite opening up its interior it was still tight) and puts too much pressure on the thin walled housing. Small cause big effect.
In order to fix this problem I decided to mill out the crack so its top becomes a V-shaped groove that can be sealed with epoxy. The picture below shows part of that effort:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4831_zps1pvyixow.jpg)
Further inspection showed that this crack had already propagated way beyond the feed through area:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4834_zpsw57pik8o.jpg)
My friends in the shop then used an end mill to produce a V-groove along the entire length of the crack:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4836_zpsfydteqts.jpg)
The work area was freed from debris and paint residue using a steel brush and acetone:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4838_zpslgz5v9ey.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4840_zpsg3rglzrq.jpg)
After that we applied Miller-Stephenson two part epoxy 907 over a wide area to promote adhesion:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4841_zpso98ccrlb.jpg)
Let's hope that'll fix this problem. I will probably not install the little rubber grommet with the cable to keep any stress off this area in the future.
I've also pressed-in a new crank seal into the left housing, using the orientation identified here on this site:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4845_zpslbnigv6q.jpg)
I'll start re-assembling the engine today. Let's hope it'll work right this time!
Cheers
Andreas
My choice would have been to have the case welded. I weld magnesium frequently, easy to do if very, very clean.
Hi All,
I installed the left crank seal, have a look at the image:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4869_zpsxj3imwib.jpg)
I sits in there straight, shows no deformation, the lips are free of any imperfections. Hope it'll seal now! If not then I simply don't know how to do this.
The left crank housing oiled for insertion of the crank shaft and the transmission:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4866_zpsb7xhzfkb.jpg)
I oiled the piston (has two lubrication holes on the outlet side):
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4873_zpsmfhnnhia.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4875_zpsnrqwykvx.jpg)
Transmission inserted. I've rarely done a more fidgety task than this. There seems to be always some part that falls off or is misaligned when doing this.
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4880_zpslfunoti4.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4886_zpskdacrt1s.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4889_zps1mpbmlh7.jpg)
Next step: put the cases back together. Given how much tough luck I had the last time around with the leak tightness I will use an elastic sealant this time to help seal the housing. The paper gasket is awfully thin and this may help getting this tight!
Wish me luck!
Andreas
I'm with JP, I would have installed crank seals that are all rubber. I have never used one's with the metal outer. I would think you would have a better chance of sealing with the rubber one's
It's in there now! I got the seals from Al Buehner, usually his stuff does work, I have to say. Let's see how it will come out.
I've put the crank housing together today, using elastic sealant (Yamaha brand Yamabond 4). As next step I'll put the cylinder and head in. After that I'll pressure test the engine on the bench. The left seal is still visible from the outside at this point as the left outer bearing isn't in yet. I hope that with a flash light I'll be able to spray both crank seals with soapy water and unambiguously find out whether or not the seals are tight.
Cheers
Andreas
Hi All,
I put my engine case together yesterday with a new gasket and applied elastic sealant (Yamabond 4) to both case halves. I did the same to the base gaskets, installed the correct deck height and put the cylinder head back on.
Today I measured the rate of gas loss by pressurizing the engine. The pressure-time dependence is exponential, so it seems the correct description is the length of time it takes to loose half the gas pressure. Starting from 5 psi when testing, this time is now 5.8 min compared to 2.0 min before this rebuild. I didn't check for any leaks but are wondering whether anybody has a real spec on this gas tightness. Can anybody give some number I can compare to?
Now comes the thing: I put the cylinder head on, torqued it in three steps (1/3, 2/3, full value) to the values given in the manual. This worked well until I got to the last stud. When going to full torque I could feel the thread giving way! Some things are apparently not meant to be; like me finishing this engine. I will have to take the cylinder off again to fix the thread with a Helicoil insert. I only hope I'll get the base and head gaskets off without damaging them. Otherwise I'll need to order yet another set.
Cheers
Andreas
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4898_zpsmbisflwg.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4903_zpsvhvxa1u6.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4906_zpslhnqnybw.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4909_zps3u1psxdb.jpg)
I took the cylinder off again. Below you can see the thread of the right back cylinder bolt (or what remained of it). This only failed in the last assembly step.
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4923_zpsfhnmi03l.jpg)
I put a Helicoil insert in to fix this problem. Here a picture taken before breaking the tang:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_4926_zpsst2unl5x.jpg)
I decided to put new base gasket in. I don't want to take any chances of repeating this yet again for saving $12 on the gaskets. Wish me luck that it works now.
Andreas
P.S.: The gasoline coming out of the carb when started always dissolved the black engine paint. This time I put an additional coat of clear lacquer on. Let's see whether this withstands the gasoline better.
Hi All,
I put the cylinder back on:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_5026_zpszokxtia5.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_5033_zpsiuyc0tcs.jpg)
This time I tightened the screws and bolts to only 80% of the torque in the manual. Nothing gave way. I hope the bolts will be tight enough.
This week was the Barber Vintage Festival. It was a great event, with a bunch of Pentons there racing.
Cheers
Andreas
Hi All,
I've leak tested the engine again after putting the cylinder on. Does anybody have a spec on the rate of pressure loss of a properly leak tight engine. It would really help me to have some value to compare to.
Many thanks in advance
Andreas
Hi Penton enthusiasts,
I don't seem to get a lot of traction with my question about an acceptable rate of pressure loss. For my engine I measured the engine pressure versus time (semi-log representation) and get:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/press_vs_time_plot_zpst3pzrw9e.png)
Would you judge this to be acceptable or indicative for a gas leak that warrants further investigation? I can't state the leak rate as I don't know the gas volume.
I would greatly appreciate any guidance you might be able to give me. Obviously some numbers I could compare to would be most useful!
Cheers
Andreas
So are you saying in four minutes you lost 2 to 3 pounds of pressure?
Ron Carbaugh
Yes that's what my measurement is indicating. Any comment?
Andreas
From my experience those numbers are very good to excellent.
Not being there and not know how much oil was on the cylinder walls it looks good to go.
Ron Carbaugh
I always used 1 pound lost in a 5 minute period was good. Anything else and you still have a problem.
Terry
I think I remember that you said that the connecting rod had been changed. I was wondering if the crankshaft runout was out of limits, could that cause an air leak at the seals. Could you test for that by rotating the crankshaft while doing the leak test?
That's a good suggestion. I haven't installed the left outer crank bearing yet, so I can even soap spray the seal. I've tried that before and didn't see any obvious bubbles indicating a leak. I'll try rotating the crank this weekend to see whether the measured rate of pressure rate changes when rotating the crank.
Thanks, make a post if you have an idea!
Andreas
Hi Penton group,
I tried again yesterday to locate a gas leak in my engine using soapy water. I couldn't find any. I tried rotating the crank and didn't see a change in the leak rate either. I re-torqued the head to now 90% of the book value and didn't see a change in the rate of pressure drop when doing repeated measurements. Given that there also seems to be no clear spec out there for an acceptable rate of pressure loss I decided to put the engine back together now. Here you see the pressure-time dependence I have: the time constant of the drop (the fit line shown is an exponential, determined by Excel) is 7.1 min.
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/press_vs_time_plot_2_zpsamjydnrv.png)
I also decided to install "new" fiber friction plates in the clutch:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_5044_zpswsmsiduq.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_5047_zpsqcmwulwa.jpg)
Let's hope it'll work this time around!
Andreas
Hi all,
I put my engine back together yesterday:
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_5066_zpserprsb6a.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_5067_zpsuzbznnbs.jpg)
(http://i1341.photobucket.com/albums/o746/andreas_g_piepke/Penton/100_5079_zpsmmrqu88v.jpg)
Let's hope it'll work well this time!
Cheers
Andreas