Cam skipped a tooth?

i just need some confirmation on this one. Took my valve cover gasket off because I had terrible compression on all 4 cylinders (90-110) and it would drop quickly on all four. So I checked the markings and while my exhaust cam marker lines up nice my intake cam marker is not lined up (see pic) however, I don't have the book (already ordered and on its way) so I don't know if these are cam timing markets or not. It's just an assumption. So two questions really. Are these markings for the timing? And if so how do I know if the exhaust cam skipped and tooth or the intake cam? Thanks in advance!!

 

Yes those are the marks for timing the cams in and no, that is not normal. Is this a new project bike for you or was it a runner?

 

The allen cap screws are interesting on the caps too. What bike is this?

 

Ok I figured it wasn't normal I just wanted to make sure. And It's a 1982 SECA 650 with 13k on it. Bought it for 800 not running and got it going last spring but it never quite ran right, (felt like a 250cc honestly) I just ran it around town last summer but now im trying to get a head start on it and fix all the issues it has before it gets nice out. Ive recorded all the valve clearances and shim numbers and will be ordering those as well shortly. most were tight but no that tight. Also rebuilt the carbs last year but the #1 carb keeps leaking gas into the #1 Cyl. so thats another issue.... And im slowly leaking oil out of my head gasket so I'm working on that as well. Its a work in progress thats for sure.

 

This is what I'm working with.

 

That's a good looking bike! The manual will cover the procedure to get the cams timed in correctly. I'm not surprised it ran like crap. I have a full set of the original cam cap bolts if you'd like them, PM for details on that.

 

Thank you! I always get compliments on it even if i'm just getting gas haha, two people have even offered to buy it from me! Its cooler to me then what its worth though. I have no plans on selling it. I was also so close to taking it to a shop and just saying fix it but I figured even if I make mistakes and learn the hard way at least ill still learn yanno? When someone else fixes your bike you know nothing when you drop it off and nothing when you pick it up. I just hope its ready to roll by the time it gets really nice out hahaha.

 

free down load haynes 650 and 750 manuals
XJ750 manuals

 

guess you have to ask yourself why the cams are out of sync?
is there a master clip in the timing chain?
could be your cam chain tensioner has failed
could be the po thought he could adjust the cam action.
there are or were after market adjustable cams

 

My bet is PO goofed up/ hadno manual. Cams have definitely been out judging by the different bolts on the caps. If the tensioner had failed, she would rattle and roll with the best of em.

 

You definitely got the right attitude towards repairs. I'll do the XJ broken record and remind you about old brake lines, delaminating rear brake shoes, etc. That's all important too when barreling down the road after it warms up.

 

+1. There's a section of the procedure when installing the cams, chain and tensioner where the engine is rotated and a wrench is used to individually align the dots on the cams with the markings on the caps.

Gary H.

 

Yup, someone has been in there, and screwed things up a bit. No wonder it doesn't run right.

Nice thing is-- when you're all done, your gonna have one HECK of a bike

Now, you checked and recorded shim clearances and sizes. You DO need to finish that job and get clearances back in spec. Out-of-spec is out-of-spec. "Tight but not that tight" is still tight.

I bet your 650 Seca will be running again before mine is... Lol

 

Hey Hogfiddles, I'm pretty sure you helped me clean my carbs last spring! Even though it was an awesome learning experience you can imagine my frustration when I could NEVER get it to run better then my dirtbike..... hahaha I shouldve dug a little deeper to see if I had any other issues hidden because of dirty carbs. but the good news is I can get my carbs off in abouttttt 4 minutes now. lol

And yea I'm absolutely gunna buy the shims I need to really get it dialed in. My top end gasket kit is on its way already I just need a few more things new plugs, oil filter, (oil), air filter, tires, and shims. And from what ive been reading new break lines too. I hoping its up and running in 2 weeks. I'm already planing a nice little road/camping trip when its up and running right. On a side note: where do you guys buy your tires? finding our my size tire is like next to impossible.

 

you just saved me 40 bucks!! Thank you! what an awesome find.

 

and you do not have to wait for it. think of it as 40 bucks you can buy parts with.

 

Imo make the engine a solid start, off and re-start affair then attend to the other stuff (i.e. the starting and charging systems).

Gary H.

 

update: So I put her back together (left carbs off) and checked compression with less than ideal results. I'm hoping its a busted gauge so im picking up another one today but across the board im getting nothing... I mean, itll bump up to like 20 lbs and drop immediately. Whats strange though is when in put my palm over the intake boots its feels like a lot off pressure. It sucks my palm in pretty well. I also checked the gauge off my well running jeep and it would bump up to like 90 lbs and drop to 0 within 5 seconds. I was talking it over with the old man and he brought up a good point that it might be possilbe that i set the cams up 180* wrong? cause ive made that mistake on my camaro in the past but i dont know if thats even possible on a bike motor.

 

It sounds to me like your gauge is suspect judging by the test on your Heep. I have two of those bikes- one runner and one for parts.

 

Agreed. It's the gauge. Maybe the schrader valve is shot so it drops pressure.

 

Borrow a GOOD gauge, them let us know the results

 

ok so not the gauge.... which means my jeep might need some help too lol. but thats besides the point. So two things I possibly messed up. One: I set the #1 piston to TDC but after reading the book i see now that it might actually be slightly different becasue there are markings to set the crankshaft to over by where you turn in towards the bottom of the engine. so im curious to see where that is when i go home tonight. and Two: According to the book there are rubber o-rings that go around the cylinders. Now i did get them in my top end rebuild kit however when I took the original gasket off there was no evidence of rubber o-rings and there is no grove to set them in so I set them aside. should I take the head off and put them in? Thanks in advance guys!! Also called a bike shop to give me a ball park est. cause I felt like I built off a little more then I could chew and he said minimum 1,000 bucks. So im in it for the long haul on this one guys! lol

 

If you mean the red o-rings, they go underneath the cyl...... Here's an example---

 

Given recent trends, I have to ask where you got the gasket set from.

 

Yes those are the rings I'm talking about but I just took the head off. Ididnt get that far down the engine, The pistons are still in.

 

I got them from chacall. I have a new theory thought which im gunna check out tonight: I think that separate gasket that goes around the cam chain may have moved slightly and got caught up on top of the other gasket. Its coming back off tonight. I'll let you know what happens! Thanks guys.

 

Those O rings wouldn't cause a loss of compression, just a possible oil leak.

 

What separate gasket ? from top to bottom (apart from some oil gallery o-rings) you simply have => Valve cover (rubbery thing)=> head gasket (metal sandwich thing)=> Base gasket and orange o-rings. Your low compression could be stuck rings since you have the gasket set I would take off teh barrels as well - you can then also check for bore wear..

 

The gasket I'm talking about is the cam chain tunnel seal. #19 in the book on page 55. And I thought about taking off the barrels too but I don't want to make more work for myself. I can still see the cross hatching on the cyl. walls and I don't see any scoring or scratching on any of them so it just felt unnecessary. Also what seems to be confirming my suspicion about the gaskets not seating correctly is that cyl. 2-3 have 0 compression.... like, you can put your thumb over the spark plug holes and feel nothing. However cyl. 1 and 4 have ok compression relatively speaking of course. at least with those I cant hold back the compression with my thumb although my gauge still confirms that they are maxing out at about 90psi and drop to 0 in about 4 seconds. I'll post my results tonight.

 

There is a rectangular gasket that goes around just the cam chain tunnel. Looks like this:

 

yea thats the one I put in there. I'm thinkin it may be caught up on the other gasket though. I'll find out tonight after work. I hope thats my issue cause if not im going back to the drawing board. maybe rings?! ill keep ya posted!!

 

Ok my bad - figured the top-end on these engines would be the same at least ..

 

Just wanted to put this thread to rest incase anyone was following it, I got it running! Took me a while to get the timing just right but the head gasket brought my compression up and stopped my oil leak. The bike runs better then ever! It finally feels like a 650. Thanks for everyone's help. That was a big project but making all those mistakes was a huge learning experience and now that I know how everything comes apart and how to put everything back together I could probably tackle this job in about three hours. Now just have to get my valve shims adjusted and she'll be 100%! (And some new tires... Lol)