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The rebuild saga continues . . . .

2216 Views 24 Replies 4 Participants Last post by  texmawby
Interesting day. These photos may not be in order, but here goes.

1. I found out what the problem was at the track. The F#$%ing screw came out of the oil filter, which was the SAME issue that caused the original seizure issue with Strempher et al. So I have screwed it in in with red locktite; See what it did to the oil cover. Totally screwed it up. It was only the tab on the lockwasher on the oil cup that saved the oil cup from flinging everything everywhere.

the engine received a full wash out with solvent and a few changes of oil.

2. So following JB's advice (HAHA) I decided it was time to put in the SHINY NEW PISTONS. Woo Hoo. Fit like a dream. But I did put them in by installing in the barrels upside down and then putting the pins in the rods with those ultra coll JB supplied connecting rod pin buttons..

3. I went with a stock cam (for once) with standard side covers. I will do with that for a season just to get this fu*&^ing thing runningf!! I am saving the needle bearing covers for that special moment.

4. I also used loctite on the oil pump stud nuts, as they seem to be losing their correct thread.

5. something weird happend. I put the pin on the cam down, the "O" was up on the cam, crank at TDC, and then i put the cam chain on. no problem. finished assembly. Drive chain on, carbs on, fuel on, etc. . But it wouldn't fire. All I got was instant backfire, which I knew was timing was off. So I put the Pertronix 180 degrees off from where I've been running it. Fires up perfectly. Very strange, I haven't figured this one out yet. JB??

So here (I hope ) are the photos of the fucked up oil cover thingy, and the shiny new pistons.

By the way, the bike runs GREAT. Now I just gotta keep checking stuff. Notice the sleeping dog in the photo.

Aaron, make SURE YOU PUT THAT lock ring behind the oil slinger thingy.

This photo also shows, if you look carefeully, where the cam chain made grooves into the head on the forward lower side and the baddy bladdy bladdy [it's getting late}. . . . Jesus *&^

But Larry 888, thanks for the racing on the presums. today. It was a blast. A little known secret. And that Honda 125 was a hoot. You should try it. And you were scraping pegs!!!!

Uh, did i get the pistons in the right direction? Aren't the spark plugs on the other side?

I'm gonna run this fucker at the streets of Laconia and shit. . . .
Edited by - imslow on Jun 04 2005 9:40:27 PM

Edited by - imslow on Jun 04 2005 9:41:17 PM

Edited by - imslow on Jun 04 2005 9:43:01 PM

Edited by - imslow on Jun 04 2005 9:50:24 PM

Edited by - imslow on Jun 04 2005 9:53:45 PM
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No real ideal on what the timing issue is...unless they changed the position of the pin on the camshaft between different model years. Or unless some pressed off the sprocket and rotated it 180 degrees....don't even know if that would do it. On a pertronix with two magnets it shouldn't matter if you move the pickup 180 degree since there are two magnets and it fires both cylinders each time I'd think it should work either way. Pin on the cam must be in a different location than the previous cam?

Clay those pistons with that stock cam...I've never tested those pistons with a stock cam...I'm guessing there should be more than enough room but always best to check and write down what the clearances are. Plus...if you have the room run a .043" head gaskets...with the added compression and a stock cam it should make some real good torque.

On that oil filter cover bolt...I always replace the OEM bolt with a Stainless socket head. Did the crank nut loosen up too? If it did, you might want to keep an eye out for unusual amounts of vibration...kind of strange for both of them to loosen up like that. Might point to a problem with the crank.
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If there is ANY...I mean ANY...radial (up and down) movement of the crankshaft at any point then it's trashed.
There will sometimes be a couple of thousands axial movement (side to side) that doesn't seem to hurt too much. If there is more than a couple of thousands axial then you have to find out of it's the bearing shells moving in their saddles (can often be cured by retorquing the main bearing bolts...or if the movement is inside the which case the bearings are trashed.
The spec for radial runout on the crank is about .003" in one revolution as far out on the taper end as you can get the dial indicator. ANY radial movement of the crankshaft at the bearing is a sure sign the crankshaft is about to go. If the outer bearing shell moves up and down with the crank then the saddles are trashed and a new set of cases is in order.
Is that the same crank that came in that engine? From what I saw of the engine at Pete's I would have just replaced the whole thing for the most part...just keeping what parts were usable. These cranks are very very tough...if they show any bad signs it means they are cooked and need to be replaced....easy enough..any vert or sloper crank will do.
Just find one where the side to side end play at the small end of the rods is about 2mm or less. Spec limit is 3mm...that's rocking side to side, not sliding side to side.
Seriously...if you can jog the crank up and down at TDC any at all then the crank is going to beat itself to death in short order.

PS...the reason there is movement at TDC is because there is where the greatest stress on the crank TDC and BDC.

Edited by - jbranson on Jun 05 2005 5:00:03 PM
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Not sure what you are trying to say, but the crank should never ever ever have any radial runout at the bearing at any point in the rotation.

TDC and BDC are the high stress points because the crank and rods must absorb energy of piston deccleration as it comes to a complete stop at TDC and BDC. Calculate the piston speed at 12,000 rpm and then realize that at TDC and BDC the piston most come to a complete stop and reaccelerate to peak piston speed in a tiny fraction of a second twice for every revolution of the crankshaft.

If you are talking about the fact that the crank moves a bit at TDC and BDC without moving the piston....then that's not what we are talking about....we're talking about radial runout of the crankshaft. Or freeplay in a direction perpendicular to the axis of rotation.

Scott, call me if you have any questions. If your crank has runout at the bearing the engine is going to explode. These things aren't stock CB350 engines...they are making close to twice the stock hp and turning 3k rpm over the stock redline, they will not stay together unless they are right.
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They balance out the forces at particular rpms but the bottom line is that it's reciprocating mechanism...the counter weights rotate...the piston moves up and down. The forces of the piston changing direction must still be absorbed by the crankshaft and rod bearings. The only real way to counter balance the pistons is an opposed cylinder engine....and still they are applying twisting force the crankshaft as view from above because the rods attach to the crank at different locations.....except for engines with siamesed rods.

Basically that's why cranks in reciprocating engines can't be truely balanced...they can be balanced at a particular rpm, but not over the whole range as the forces generated by the piston changing direction change at a different rate than the forces generated by the rotating counter weight.

Anyway....if you have any radial play in the's gonna blow up. If at any point in the rotation you can feel play in the crankshaft in the radial direction (up, down, front, back)'s definately, positively, most assuredly dead.
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Why ruin the whole engine. If the crank goes it will probably trash the cases too. And maybe that pricey set of pistons.
Building a real race engine isn't easy. I spend a lot of time with a dial indicator, granite surface plate and micrometers before I put anything together.
The engine isn't was probably just trashed when you got it. Every tear down you gotta check all the bearings, rod play, crank end play, cam bearings, rocker pads, oil system etc.
Treat it like a MotoGP engine, that's the level of stress you are putting on these old engines.
If you are talking front to back, or top to bottom play...along the radial plane (so any direction but side to side), then .005 is trashed..I hate to be the bearer of bad news like this but any slop at all in the crank at the bearing is very bad news. The spec for "run out" at the begining of the taper is .003"...and that's rotational runout...meaning it's checking for a wobble in the crankshaft. Radial play at the bearing is a whole different thing, it indicated either a trashed crank bearing or main bearing saddles in the hand I'd guess it's the saddle in the cases....but it will soon be the crankshaft too if you run it that way.
If the original crank had about .020" then it most probably ovaled out the main bearing saddles in the cases. Most saddles I've seen do show a bit of wear in the saddles...usually from side to side movement in the crank and the bearings just settling in.

What you want to check the cases for is ovaling parallel to TDC and BDC.

If you can move that crankshaft up and down by hand, or produce any "clicking" by applying up and down force on it with your hand it's a goner. Radial clearance on the crankshaft is probably the only practically zero clearance you will find on an engine.

If you do decide to blow it it, then by all means put some 20-50wt oil in it to cushion the main bearings as much as possible....normally oil doesn't flow between the main bearing shell and the saddle..but if you have clearance there it will try to seep in there and that may soften the impact some.

If you race it, it may trash the oil filter cover and access cover again. At race speed it's probably moving around about .010" or so.

It scares me seeing a dremel tool turn 12,000 rpm...and you are turning a 15 lb piece of metal that's got to be right.

On the other side of the coin....I've seen these engines accept some tremendous abuse before they give's possible it will last a race before it kills the crank, cases, cam and bearings :)

Come one is not just thrashing a bike around the's a Zen excercise in patience and precision. An engine that you built failing is like your dick not should be a humiliating personal is for me when one goes. least some of you guys are using your own dick....some people limp around with someone else's dick all the time, never realizing the full glory of victory with their own, or the full humilation of defeat.
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Haven't heard from Aaron. Sent him a cam and bearing, he must be hard a work putting it together.

I've decided to give Beaver Run a miss....sounds like it going to be a circus....literally.

Might make Shannonville instead.
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