My Six Day....Top End Rebuild Advice sought

[tooclose racing]

I have to re-check my set-up on the TTR, but I've just done a compression check on my 6B motor and the results are...0 lbs. compression.  Nada. Nyet. Zip. I checked the gauge against compressor so I know the gauge is working.  I'll recheck on Monday (we're packing to get out of town in an hour), but I can hold my thumb over the opening and there is no pushback/force...or at least very little.

And yet I finished 4 motos at Broome Tioga! (Cue Twilight Zone music and Rod Serling walking under my 10 X 10 with the my bike in the background and me frozen in horror)

If you read my racing post, you will know I was looking for my moped pedals on the hills and any straightaways. As I also mentioned, I started short shifting on the straights (on a freakin' 1-2-5!) because there was no top end at all, but on one straight she actually "signed off" momentarily and came back on.

Hmmm...okay experts, realize top end needs to come out for inspecton/measurements, but am I going to get away with a honing and fresh set of rings OR would you wager I'm looking at going up a size to make this right?  

Thanks for your thoughts....

Happy 4th of July weekend!

[Larry Perkins]

Check the head gasket.  I bet you blew it.  Check the piston to be sure rings did not stick but my bet is on the head gasket.  If it proves to be the piston then bore it and be done.  Don't re-ring.  Be totally fresh and know where you are.

Larry P

[tooclose racing]

Larry - thanks for feedback. wouldn't a blown head gasket be obvious, e.g. dis-coloration at head/cylinder joint?
 

[Larry Perkins]

Most likely.  Especially after running a bit.  I had it happen recently; though, and it was not real obvious till removed.  I thought the motor went South but it was the head gasket.

Larry P

[tooclose racing]

Oh geez, I'm in over my head now!  [:I]

Both gaskets look good, some slight discoloration on right side of cylinder beneath transfer - almost looks like NOT worn, the piston has cast-in or machined ridges beneath/between/above rings. These ridges are worn away/smooth at front of piston to right side of piston top above and below first ring, some light vertical wear also on front of piston.

Overall, doesn't look as bad as I would have thought given compression check results.  Ports are stock (hey - if it was ported I'd have some REAL explaining to do to y'all for my results), very clean.

I can have a machinist (yes...at my nuke station) do some dimension checks first thing in the morning - still waiting for "local" cylinder boring/fit-up recommendation from fellow vintage racers.  I want to confirm where I'm at and what I need to order (i.e. I see kits listed from 54 to 55.75 at Al B's sight).

I've subscribed to the Penton tech site (BTW), but any feedback on what kind of dimensional checks to do now and suggestions for how to go up in size based on what we find would be appreciated.

BTW - remember the "blown" Red Wing shock I mentioned in my race blog?  Well, it was just a loose cap..I had a local shock rebuild guy (Shockaholic) take them both apart, get rid of the fish oil inside, clean them, and rebuild/fill with his suspension oil (Golden Spectro I think).  He charged me a small fee, said I should really think about a nitrogen-charged shock for MX.  Cripes...did you guys get to him first?

[tofriedel]

Bob,

I sent you an email regarding your repair.

Tony

[tooclose racing]

Based on cylinder measurements, ordered 54.75 piston kit (Wiseco)and new base/head gaskets from Al B. Also located very experienced two-stroke racing shop for boring/fit-up. Heck, the guy asked me if I had any porting specs/needs (yea-i know there somewhere here on the site-but  I'm still new to all of this). Anyway - In Monday, done wednesday. Together and running by weekend for some break-in time. I'm going to grab a few more main jet sizes - not sure I'm right yet since switching to the Circle F pipe. So far, so good in terms of being ready for VMD.

And let me just mention that I received a SHOCK e-mail from WP shocks (Blue light special thread..). My MC5 shocks shipped on Friday, four days after ordering. Maybe it's a little slow out at the "factory" with the economy, or maybe I just hafta send them my Customer Service of the Week award.  I was going to give it to Al B., but when I asked if my 5th purchase from him would be free (hey-Penton. Parts Club special, right?), he said "Uh..No." Imagine that.

[john durrill]

tooclose,
 Was the piston installed 180 degs out? This one is a poser and keeps popping into mind all day !!!!!!!! [8D]
John D.

[tooclose racing]

No John...hate to disappoint you! Remember, I've done 16+ motos (I finally added them up), with 4 of them in some really muddy conditions.  If I add in practices - I'm north of 20 motos on this 1-2-5.  I took my cylinder and new Wiseco piston kit (thank you, Al B) to Bristol Racing today - a genuine old school racing shop.  My eyes teared up just walking into the  place.  Sure, he's keeping up with the moderns and technology, but...I dunno.  As in...I dunno how this guy stays in business!! The gentleman (I'm such a jerk I didn't ask him his name) looked at my upper ring, the worn-away front on the Mahle piston (were these OE?), the cylinder, and said "uh - looks like you are getting some pretty serious blow-by".  I asked about my engine running rich at Broome and he thought that the leakage results in a pretty "soupy" mixture in the crankcase/transfers.  Which means..."rich".  What do you guys think?  Makes sense to me....

We then went "back in the day" (he was maybe in his late 40's I'm guessing)and he talked about remembering how many Pentons/CZs, even some Bultacos and Rickman-Z's in the 125 class until...the Elsinore/YZs showed up. He said it was like overnight and suddenly the Pentons were far and few to be seen in the 125 class at the MX tracks in Central NY.  Sigh....

Anyway..great guy.  Suggested I leave jetting alone until broken in, and then see what the Circle F pipe is doing (or not).  Will pick up the pieces and put it back together this weekend.

Sorry Tony..haven't found the CD/manual yet. [)]  What should I torque head nuts to?  And one more thing...is it just my imagination, or is the right rear nut on this Sachs head/cylinder a complete pain in the a__ to access?  Holy cow.  I know I gotta go back to store and find right extention to work with my 10mm Allen snap-on.  

BTW - this is my vacation week. I've clocked a 1 hour + mountain bike ride every morning since Saturday. Muddy, scratched up calves, went over the handlebars twice.  I freakin' love it!  Poor guys at VMD CC race - they'll never know what passed them.  The restored toaster tank - replete in Six Day Green - will be going back on bike for the Friday CC race.  Let..them...pray!

[thrownchain]

Guys name is Rich, good people.

[tofriedel]

Bob,

Off the top of my head, I torque the head bolts @ 18-20 ft/lbs.

Tony

[Ernie Phillips]

Bob,

22 ft-lb

I use a "wobble" extension. -- see below



Be sure and radius the port edges.  Your ring life is way too short. Maybe the mud got to it.  By comparison, we run the dog s*** out of our rigs.  My primary bike has 1-1/2 seasons on it, moto-X  & CC & ISDT-RR and still has 150 psi (down form 165 psi) compression including muddy races at Diamond Don's, Tomahawk, SC, Combs – but I didn't suck no mud!  On the other hand, Christopher's hundert' is down on compression because he sucked water/mud at Tomahawk.  But, he has still been able squeeze some performance (1 year of racing) out of it.  (Engine will be rebuilt in a couple of weeks though.) Thinking way back to 1971  – my brand new steel tanker went a whole year on the original piston/rings.  The bike got ridden almost every day, raced on weekends and maintained by a punk kid ... Quality components, properly fitted and maintained, will last a long time.

Yes, bad piston/rings effects how the engine sucks & blows and screws the jetting up.  Good luck at VMD!!!


Ernie P.
Chattanooga, TN

[chuck]

Sounds familiar to a problem I had a few years ago. Turned out my exhaust pipe had carbon build up. Used a MAPP gas torch to burn the carbon out. Worked great afterwards.

Good Luck,

Chuck


72 125 Six Days
72 100 Berkshire
74 250 Hare Scrambles
72 Wassel

[tooclose racing]

Ernie - big thanks on the swivel recommendation.  Should go together much easier. And thanks to both of ya (Tony/Ernie) for torque #.

Very interested in post-rebuild compression number.  And obviously now I will have a base-line "here's where I'm starting from" as I go forward from this rebuild. I can't remember if I've asked Tony or not about history on motor before I picked up bike in May of 2008.  

Registered today for VMD "Sportsman" 125 class on Saturday and Evo 1 for the MC-5 (same day).  It will be interesting to see if these not-so-friendly-to-Pentons class ends up being an Elsinore-fest.  I guess it will also be interesting to see how much "Youth of the Nation" is present on these MX starting lines.

Also obviously signed up for Vintage 200 class for Friday Hare Scramble/CC race.  

[tooclose racing]

Break-in has commmenced!  Got her together and the 6B fired on 5th kick with a fresh batch of gas/oil and new plug.  But never, ever let me work on your motorcycle my friend.  My antics in the garage would probably get Superhunky (from Dirt Bike mag) all misty-eyed - but the rest of you would probably just say "Bob...slowly hand me the wrench and keep your hands up".

Wiseco piston circlips - hello?  Could they make these any less friendly?  Basically shaped like the letter C with nothing to "squeeze" for compression.  The piston does have an indent to help gain access to the groove the circlip sits in, but that only works great if you are getting one out! And THEN I couldn't get the second one  to seat properly, which I could tell because I was watching the gap between the two ends, which was much smaller than the gap on the other properly seated circlip.  I won't mention what I used (gently, I promise..)but I did finally achieve the proper seating.

Wiseco piston rings - Pretty straight forward, but the locating pins are in the exact same location  - 180 degrees from front of piston.  My logic was telling me this provides a "leak" path, but what do I know?  Piston at bottom of stroke.  Squeezing rings from the sides (lightly oiled piston skirt only per Race Shop), I get her down over first one ring, then the other.  And realize I am staring at my exhaust port!!! It's on backwards.
Cripes. Easy does it back up...look around for hidden camera..180, then back down.  First ring....then second ring...easy....WAIT..I didn't SEE the first ring capture the locating pin.  Try to look down intake port - uh, Bob, the rings don't go below the intake port dude. Ease it back up...it occurs to me after raising it off of the rings that the rings won't seat if they aren't capturing the pin, but one more time..squeeze from sides, and...we're...good with both pins, seated, a couple of gentle rotations with flywheel, and ready to install head/head gasket.

Torqued up nicely, thank you very much.  

Reinstall carb, clean inner air box and boot till I can eat off of them, wash and oil filter (I use the Maxima products) and install with cover.  Re-install Circle F pipe.  Which took 2 minutes to snake in first time, and takes 15 minutes this time.  Go figure.  I use the supplied spacer/rubber mount (along with 1/8 " thick rubber washer) for the right side and NOW get nice clearance between silencer/tailpipe and shock.  Back on with the rebuilt Red Wing shocks, button up this, cinch that, mix up fresh batch (1 gal) of gas/oil about 40-1 and I'm done.  And it's 8:00 with the sun fading.

What a beautiful sound when she fires.  I give some light throttle tweaks for about 5 minutes and then kill it.  I quickly threw on my jeans, a riding shirt, helmet, and Totally Inadequate tennis shoes - fire her back up - and head down quiet neighborhood street to end of cul-de-sac and beginning of my very overgrown (we've had a ton of rain up here) local trails. Which suddenly seem quite tight on the Six Day, but she stayed clean and I kept RPMs low-to-mid throttle for next 20 minutes until it was too dark to see.  

Back to garage, open cold beer, and breathe huge sigh of relief in terms of VMD readiness preps. We'll put another half-hour Monday or Tuesday on her before winding it up and seeing where the jetting is at.

Thanks for your help and input, POGGERS!