Cam timing questions...

[Mustangsean]

Hey all, I just picked up a 1980 XS1100, and have some real questions about its behavior. Here's the short story:

When rebuilding the engine, I installed a Wiseco 1179cc overbore kit, along with new gaskets, etc. Following the instructions in the Clymer manual for valve timing, when starting the engine it sounds as if the valve timing is off. The engine does not spin over evenly, and when attempting to start the bike, it backfires through the carbs. I've checked, rechecked, and triple checked the valve timing, and everything lines up perfectly. The dots on the cams are pointing to the arrows on the caps, I'm aligning the pointer with the 'C' when installing the cam chain tensioner, and after rotating the engine over a few times, everything is still in alignment.

I've come from a background of cars, have many motorcycles, and know I'm not crazy, but this thing acts like it's out of time.

Any suggestions??

Sean

[trbig]

First, I'd check the compression. Also, have you checked your cam to shim clearances? Did you do any head/valve work to the motor? I did a light hand lapping of my valves a while back and just that changed things 2 shim sizes.

If everything is in time, you have some valves not closing completely for it to backfire through the carbs. Hopefully the valves didn't get bent somehow during the installation and it is just the shims that are keeping the valves open.

And just to be sure... when the dots on the cams are aligned with arrows on the caps, the timing marker is on the "T", not the "C".. correct?
Tod

[Mustangsean]

Haven't checked compression yet, but suspect that's not the issue. When setting the cams, the pointer was on the 'T', not the 'C'.

Haven't checked valve lash...I suppose too tight could cause some of the problems. It really sounds like cam timing from the way the engine spins over. It spins fast, and then slow, and fast, and slow.

Just thinking about it, I think 1 & 4 were pulling a good vacuum, and 2 & 3 were not, so that may lean towards valves hung open.

Anyway, you guys are the XS experts, not me. So I'll take any advice you can give.

Thanks!

Sean

[trbig]

A motor turning fast then slow can be timing.. but could also be rotating through the 4 cylinders where a couple have compression and a couple don't. I just bought another bike that has no compression on a couple cylinders, but also has zero clearance between the cam and shim.. so it's holding open the valves.

As far as timing though... if you find you have compression... if you remove the timing plate under that left sidecover where your pickup coils are, you will see the crank that the timing plate is attached to. There is a pin that keeps the timing plate in it's proper place that has occasionally been known to fall out. It will still be there if this is the case and just needs to be re-installed with some Yamabond or something. Here's the pin I am talking about..




I would check for compression first though. If you don't have a gauge.. you could pull the spark plug and put your thumb over the hole and see if it blows it off while cranking. Not accurate.. but does tell you if there's compression.


Tod

[bikerphil]

If you had the ignition pick up apart, possibly the projection on the timing advance mechanism could be off 180 degrees. This is the sleeve behind the c-clip that triggers the pick up coils. It can go on either correct or 180 off. DAMHIK.

[Mustangsean]

If you had the ignition pick up apart, possibly the projection on the timing advance mechanism could be off 180 degrees. This is the sleeve behind the c-clip that triggers the pick up coils. It can go on either correct or 180 off. DAMHIK.

I will check compression tonight. I did not have the pick up assembly apart ( no guarantees the PO didn't, though).

[trbig]

You also might post in your personal info where you're at. You may be in an area where somebody could help you if you wanted. Most on here work for nearly free... a meal or/and a cold beverage.

Tod

[Mustangsean]

Done.

I'm in Bartlett, TN (a suburb of Memphis)

[trbig]

Hmmm... The Elvis accent didn't come across when you type.

Welcome to the forum by the way.. lol. We'll get you straightened out at some point. Lots of smart folks on here.. but I'm not claiming to be one of them.


Tod

[Mustangsean]

Hmmm... The Elvis accent didn't come across when you type.

Welcome to the forum by the way.. lol. We'll get you straightened out at some point. Lots of smart folks on here.. but I'm not claiming to be one of them.


Tod

Yeah...about Elvis...I'll probably get flamed for this one, but I've lived here all my life (32 years) and have never been to Graceland. The closest I've come is when I had a Mustang stolen once, and it was recovered a few blocks from there, on Elvis Presley Blvd. in fact!

[thewiz]

Yup, welcome ...

Lots of smart folks on here.. but I'm not claiming to be one of them.

Now there's some BS if I ever heard any , he's damn sure one of the smart ones ... he may not be claimin' it but, trust me on this one Mustang, he's one of 'em !!

Nice town, Memphis is too !! In fact, once a few years ago ....

I was walkin' in Memphis ....
Walkin' with my feet ten feet offa' Beal ...

[thewiz]

Well ... actually, I .....

Yeah...about Elvis...I'll probably get flamed for this one, but I've lived here all my life (32 years) and have never been to Graceland

.... Saw the ghost of Elvis down on Union Avenue ...
Followed him up to the gates of Graceland ....
Watched him walk right through ...

I'm loosin' it, I think ???

[trbig]

he's damn sure one of the smart ones

Well.. He has HALF of that word right..

So what did you find out?


Tod

[Mustangsean]

Took everything apart again, put it all back together, and it works. Didn't change any settings, and everything was in time when I started, but it works now... oh well!

Thanks for all the help, y'all!

Sean