Can't get it running

[454MRW]

There is a crankshaft case drain Allen screw directly under the centerline of the crank to allow draining any pooled fuel. Mike


Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Rain Man]

Anybody got 2c I can borrow?
 My favorite bog problem mistake was the little dust wipers left in the intake and exhaust ports. [:I]
How's your base compression anyway?  Near impossible to check that one I know...
 Got a big hill to push it down?  If the crank seals are suspect, it might start with the piston speed way up there...

Raymond
 Down East Pentons

[Andreas Piepke]

Hi All,

BINGo! Steve had the right idea. Indeed, I had the needle and its clip installed above the plastic holder instead of under. Looking at the parts list this is obvious after Steve pointed it out. I fixed this issue and the bike starts much easier and revs up when in neutral. Have a look at the little video I've posted:

http://youtu.be/pmjiYrEN3pA

Now with this problem fixed the job still isn't done. The bike doesn't rev up when put into gear. What you can see in the video is about the top speed I can achieve. So something still isn't right. The bike should be a little more lively than a moped, I guess.

Keep on analyzing, this gets me on the right track. Thanks again!

Andreas

[SouthRider]

It sounds loaded up, and it seems like a lot of smoke from the exhaust. Too much fuel/oil or not enough air....

Couple more shots in the dark:

Any chance the clutch side crank seal was nicked when installing the crankshaft? Is there oil around the exhaust port or dribbling from the supertrapp? If yes - pull the clutch cover & see if you smell gas in the crankcase oil.

Do you have the supertrapp nuts too tight? The discs should slightly rattle when tightened correctly. There should be no other spark arrestor in the system when using a supertrapp. You can also try running without the discs & end cap. With the discs removed try blowing air through the exhaust & check the output.

Are you sure the carb floats are working correctly? Metal or viton tipped float needle? If metal - reseat it by gently tapping it into the seat with the eraser end of a pencil. Before the viton ones came out we had to do this trick regularly to create a new lower seat. Check the float level again by removing the bowl while the carb is still mounted & turning the petcocks on.

Any chance you mis measured the fuel/oil in your pre-mix?

_____________________________________________________________________________________

"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

[Andreas Piepke]

Hi Clark,

Thanks for sharing your ideas with me. I am responding below.

Cheers

Andreas

quote:Originally posted by SouthRider

It sounds loaded up, and it seems like a lot of smoke from the exhaust. Too much fuel/oil or not enough air....

>>I will definitely try this out.

Couple more shots in the dark:

Any chance the clutch side crank seal was nicked when installing the crankshaft? Is there oil around the exhaust port or dribbling from the supertrapp? If yes - pull the clutch cover & see if you smell gas in the crankcase oil.

>>I think the chances for this are minimal. I put a new seal in. On the left side you just put the crank shaft through and that's it. No alignment issues or pressing needed or anything like this.

Do you have the supertrapp nuts too tight? The discs should slightly rattle when tightened correctly. There should be no other spark arrestor in the system when using a supertrapp. You can also try running without the discs & end cap. With the discs removed try blowing air through the exhaust & check the output.

>>This is a good idea! I'll try this out next weekend. In addition I'll remove the air filter to further improve gas flow. Maybe that'll identify the issue.

Are you sure the carb floats are working correctly? Metal or viton tipped float needle? If metal - reseat it by gently tapping it into the seat with the eraser end of a pencil. Before the viton ones came out we had to do this trick regularly to create a new lower seat. Check the float level again by removing the bowl while the carb is still mounted & turning the petcocks on.

>>I had the Bing people install a new, Viton tipped, float needle. However, I did have to adjust the float level. I measured the float needle tightness and amount of fuel in the bowl by means of filling the carb with a syringe. I can put 40 ccm in there before the float needle blocks the flow. Is this too much? How much fuel needs to be in there for proper operation? I had measured this volume before changing the needle and found about 40 ccm too. But who knows whether this was correct. I find the guidance of the manual, basically eyeballing the float location, quite inaccurate, thus, the measurement of the gasoline volume (gasoline volume in there is the primary quantity of interest).

Any chance you mis measured the fuel/oil in your pre-mix?

>>No I don't think so. I was quite careful there.
_____________________________________________________________________________________

"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

[SouthRider]

We never measured the fuel in the bowl, and I don't know if that spec exists.

Rotate the carb to the side & remove the bowl - rotate it back to normal position. Turn on the petcock while holding the float up & eyeball the point at which the fuel flow stops. As described in the manual it should shut off when the floats are parallel to the carb body.

It's also possible that the engine is just loaded up with accumulated fuel from trying to get started the first time, or that too much assembly oil was used in the top end.

Get it running and keep it running till the engine gets warm. Sometimes they just need a few minutes to clean out.

I know you put new jets in the carb, but there could be trash in them from the fuel tank. If nothing else works take the carb apart again & look through all the jets to see if they are still clean (not likely as the bike does sound loaded up).

_____________________________________________________________________________________

"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

[rob w]

When there is excessive fuel in the crank case, there is a drain screw below for that reason.

[t20sl]

Posted - 03/01/2015 :  07:59:06 AM            
Just a thought. Maybe bottom end is full of gas, Try starting bike, holding throttle wide open and shut off both fuel valves. May take a minute or even 2 to use up fuel in bottom end. If it is full it will suddenly "clean out" and run fine. Then turn petcocks back on and enjoy!

Ted
 
Did you never try this?  I know you had needle too high but give this a try.
Someone also mentioned draining the crank to accomplish same thing.

[Andreas Piepke]

Hi All,

So I did some work on the bike this weekend.
1) I ran the float bowl empty three times to clear out any excess gas in the crank case.
2) I slightly loosened up the super trap disks.
3) I cleaned out the air box and found gasoline in there.

I ran the bike without air filter for a little and noted that it ran better.

4) I removed the carb to adjust the fuel level in the float bowl. As the float needle seat is a (Bing) custom part I was not sure that "float parallel" still results in the correct amount of fuel in the bowl. So I measured (on the bench) the gasoline volume that fits into the bowl until the float needle blocks. I found 50 ml and concluded this is too much. Before sending the carb for rebuild I measured 40 ml. So I adjusted the tab on the floats until the needle would block with 40 ml of gasoline in there. This now requires the floats to be a slight upward angle when the carb sits on its head on the bench.
5) I moved the jet needle from the second to the top notch. To make it run leaner.

After that the bike ran yet better but wouldn't want to take gas when transitioning from low to intermediate revs.

6) I changed the needle jet from 2.90 to 2.74 and put the needle again into the second notch.

The bike yet runs a little better. Have a look at the little video I posted:

https://www.youtube.com/watch?v=9LGQZ_XJwUI

I am still not happy as the engine now takes gas unwillingly at low revs, the transition to mid revs is rough and kind of sudden. Currently I have a type "0" slide installed. I'll try a type "2".

Thanks for all your tips. Keep on sending your observations, I want to get this run well!

Cheers

Andreas

[brian kirby]

2.74 is too lean in my opinion, especially for this time of year. Stock is 2.83, try one of those now that you think you might have the float level close. I still think most of your problems are stemming from that modified float needle/seat.

Brian

[Andreas Piepke]

Hi Brian,

I can try this. One problem: Al Buehner doesn't carry this size needle jet for a 36 mm Bing 54, according to his web page. I'll need to get this jet perhaps from Bing. Once I place an order with them I might as well get an assortment of jets. Could you advise which sizes of needle jet and main jet the prudent rider has in stock? This way I could order a bunch at once. Making these adjustments certainly improved things, I am just not there yet.

Thanks for your input!

Andreas

[brian kirby]

I have a 2.83 in my 250 and I have never had to change that for weather or altitude, I do have to move the clip position but not the needle jet itself. If you order from Bing I would get a 2.83 and the next ones up and down, which I think are 2.80 and 2.86.

Brian

[Andreas Piepke]

Thanks for the guidance Brian. I'll contact the Bing Agency people to see what they have. Another thing: I have three main jets: 155, 165, and 170. Would you recommend any other sizes?

Cheers

Andreas

[454MRW]

What size pilot jet are you running? The pilot jet combined with other jetting factors control the off idle response and I couldn't find a reference on what size the pilot jet is in your carb. Stock for the 73 250HS is a 40 pilot jet with a 165 main jet and 283 needle jet and the jet needle clip in the 2nd position according to the instruction book. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Andreas Piepke]

Michael, I am currently running a size 40 pilot jet. I do have a used size 50 pilot jet at hand. I have a 165 main jet installed. The needle is in the second position, however, with a 274 needle jet. I have already sent an email to Bing Agency to see whether they have other needle jets in stock. One more thing: my slide has a "0" stamped into its bottom. Al Buehner's web page lists type 2 slides for this model. Would you know whether or not I have the right slide?

I agree that my 274 needle jet may be a bit too small. After all the adjustments I did this weekend the spark plug is no longer wet but light brown, indicating that the mix might be a bit too lean.

The number of possible combinations of all these components is VERY large. Input from this group regarding what works is therefore a great help. Thanks for your input!

Cheers

Andreas

quote:Originally posted by 454MRW

What size pilot jet are you running? The pilot jet combined with other jetting factors control the off idle response and I couldn't find a reference on what size the pilot jet is in your carb. Stock for the 73 250HS is a 40 pilot jet with a 165 main jet and 283 needle jet and the jet needle clip in the 2nd position according to the instruction book. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R