#1 & 4 pistons not hitting TDC simultaneously???

So I just started putting my top end back together tonight. Got the cylinder on and was turning the crank manually when I noticed that the number 1 piston hits TDC slightly before number 4. I'm sure this is not normal. Has anybody else run into this??? What in the world could cause this? Is my crankshaft bent? It's got some pressed fittings in it - could they have slipped??? Am I going to be forced to split my crankcase. Would I be crazy to put it back together and run it like this? Any comments or suggestions are greatly appreciated. I'm so frustrated right now I just want to throw the engine out onto the street!!!

Cheers,

Maverick

throw it this way. i'm started a scrap engine mountain. So far 2 X 600CC water cooled 'ninja'.

Did you check to make sure your block didn't get lifted on one side? I mean what's holding it on while you turn her over?


-Duck

You don't say what the bike is. The Z1 KZ900 KZ1000 engines use roller bearing crank that's a press together crankshaft. In perfoemance engines the cranks are usually indexed (lined up) and welded to ensure they are true.

It is possible for the crank to twist in an engine where it isn't welded - although I've never known a problem with a stock engine (not that it can't happen).

It's an '81 KZ1000 (J engine). It's pretty much stock except for pods and a Kerker 4-1... I just can't imagine what could have caused this. Other potential clues: the number 1 valve seats, both intake and exhause were much much harder to lap in than the other three cylinders.

I'm not prepared to completely give up on it Duck. I'll check to make sure the block isn't shifting/sliding, but I'm pretty sure it was still... Just checked, and yep, the block is staying in the same place.

I took a picture and tried to attach it. When #4 is at TDC (about 1/2 mm below the head surface), #1 is already 4mm below the head surface.



So here's my dilemma. We're getting ready to move - just signed the counter offer this morning, and I'm afraid if I don't get her back together, things will inevitably get lost in the move. Gonna get really busy really quick and won't have time to wrench for a bit. If I don't get her back together today, it won't be for at least a month. Can I just pretend this problem isn't there, put her back together as-is and ride it for a season, then do a complete rebuild next winter (including welding the crankshaft)?

Thanks guys...

Post edited by: maverick, at: 2006/02/25 11:13

Assuming that block is fully seated in the picture, you have a twisted crank - you need to either find a new crank or get this one indexed and welded. Do not run it the way it is.

If you attempt to run the engine like this, there is a great risk you will clip a valve and destroy the engine.

I've heard of other J motors doing this - somewhat of an issue with the first year J motors

When number 2 and 3 pistons are at BDC, which piston is not at TDC, number 1 or 4?

As long as the valves don't hit the piston, I would think that you could ride it that way. I think it will probably have a little less power and a little more vibration though.

I see Jeff has already mentioned the valve issue and even posted twice while I was still typing (ok so I'm slow)

Jeff knows a lot more about the J motors than I do, so you know who to listen to

It has obviously already slipped once, so it seems likely it will do so again, and then "Ka-Boom", just something to consider.

Post edited by: steell, at: 2006/02/25 13:12

I could be way off base on these suggestions, but at this point I guess checking everything couldn't hurt.

I'm guessing in rebuilding the top end you replaced the pistons and rings?
It's not that common, but are you 100% sure that whoever you purchased the pistons/rings through gave you matching pistons (one perhaps being shorter in total height and/or from a diff model or year bike)?

Another thing that came to mind, did you check to make sure that all the connecting rods are not bent or stretched?

Like I said, I could be incorrect on these suggestions.
But since you don't have the cylinders bolted down yet, it wouldn't take much time or effort to remove them and check the pistons and con-rods.

That is a twisted crank.

That is the test you can perform with an assembled motor in the bike to see if the crank is twisted. Find TDC with your degree wheel and TDC tool on number 1, then leaving the degree wheel set. move the TDC tool to #4 TDC should be the same or the crank is "out of index", twisted.

In your case, you don't have to do that as you can see it.

Gardner racing Concepts can fix your crank.

Jay

Thanks guys...

Pistons and cylinders checked within tolerances, so I was just re-using the stock pistons. Con Rods all looked good, but I did not measure them. Both #1 & #4 are reaching the same height in the cylinder, just at different times so I don't think piston 'height' is the issue.

When the timing plate indicates 1.4T, #4 is at TDC, #1 is just past TDC...

I did a search for Gardner Racing Concepts. Look like their website is defunct, but I got an e-mail address. Jay - do you have their current contact info? Anybody out there have a (non-twisted) crank they're willing to sell???

I appreciate the advice everybody. I'm heading out to the garage to box everything up... It will just have to wait till after we close on our new house. I was hoping to get her all buttoned up today - the forecast for tomorrow is 60-degrees! Bummer... Well, beter to fix it now and have some peace of mind... Plus, when I upgrade to a big bore kit, I'll already have a welded crank!

According to APE's website it cost $79 to weld a crank, I don't know if that includes indexing though.
I'll bet there are others here that can tell you exactly how much it cost to index and weld the crank, and then you would never have to worry about it again. Probably cheaper than a crank also
Wow!! $241.00 to true and weld the crank at Falicon
Looks like it's $150 at www.billbune.com/crankshaft.html

Oh yeah, contact APE directly, don't ask for prices on the forum, don't want anyone violating the "No Advertising rule" even by accident

Post edited by: steell, at: 2006/02/25 14:41

afraid if I don't get her back together, things will inevitably get lost in the move

I'd put her back together a tad more than finger tight. Take out your battery and put a note in the battery case to prevent accidents in case you encounter a spell of temporary amnesia.

Set up your workspace at the new place and dig in..,

-Duck