Timing off - Running perfect?

My bike went into the shop about 10 weeks ago to get new tires, sprockets, chain, plugs, wires, oil change, valves adjusted, coolant flush and replace the crank seal and counter shaft seal.

When the mechanic cracked the case open he noticed my front cam timing was off. (marks don't line up) He said it is way off, but the bike is running perfectly. He is totally blown away by this because it is way off and technically the bike should barely be running. He is reluctant to just line up the marks and give it a try because he can do damage to the motor if timing is way off. He also said something about the bolts on the cam chain tensioner should be vertical, but the bolts on my bike are on an angle.

Right now he is waiting to hear back from another mechanic to see what to do...

Does any of this make sense to anyone here? IMO, this is totally against logic of an engine.

 

Yes it does make sense. How much is way off? two, four, six degrees and which way advanced or retarded? Most likely the latter. If advanced then your power band will start lower in the rpm range. If retarded then it will start higher. No big deal depending where you want to make your power. Advancing or retarding a cam or cams can be part of the tuning process of a motor. With DOHC you can manipulate the intake and exhaust separately. Which gives you lots of tuning possibilities depending on how your using you vehicle. Depending on all the other parts and there design, like intakes, fuel system, I&E ports in the heads, valve sizes, rocker arm ratios (if you have rocker arms) stroke, rod length and so on and so forth it may be advantageous to install/move the cam/s from the straight up position. If it needs more than six degrees advance/retard you may be better off getting another cam designed for your needs.

When building a racing motor this is some of the specs you have to take in to consideration. Actually all motors have the same systems basically. It's just how those systems are applied depends on the out come and what your trying to do.

Cam chains will wear and the cams will slightly retard from their original position. No big deal in most cases for a average street vehicle. For a racing motor it may make a difference depending on the sum of the parts. That's one reason for gear drives. But they bring in a host of problems themselves. Like harmonics and aggravated wear. Also depends on the sum of parts again.

Besides you already have the proof it works. You said your bike was running perfectly. You may have more top end than when new I'll bet. If both cylinder bank cams are the same and the bike runs fine then I wouldn't really worry about it for a street bike. Depends on what you want a little more low end or top end. The main concern is the piston to valve clearance. Advancing lessens the intake valve clearance and retarding lessens exhaust. Most factory motors will have more than enough for a few degrees of cam movement.

As for the bolts it sounds like they may need heli coils to straighten them out. That's a job you really don't want to have to do with the motor together unless you take a bunch of precautions to keep metal chips from falling in to the motor. You may be better off just leaving things alone provided the bolts are solid and tight.

 

Great info, thank you.

The reason it is so odd, is the front cam is off and the back cam is dead on. I was under the impression, and it seems you are too, that if you want to change timing the cams have to be the same?

 

The real easy answer to that question is yes. But with unequal exhaust,front cylinder pipes longer than rear. They should make power at different rpms. Which will be negligible to the rider. Right now you haven't felt anything thing wrong with your bike and never knew there was a problem with the cams. Your power I assume felt normal. Does it idle fine? If it does, is there really a problem?

First off I'd find out how far off the cam/s are. May be someone else replaced a tensioner and didn't get one cam in correctly which is an easy fix. Or the chain is out of spec and won't let you align the one cam correctly. If only one cam is off because of the chain, you could slot that particular cam gear bolt holes to allow you to rotate the cam back to stock position. If you do that then make a small piece of metal to fit along side the bolt in the slot under the head of the bolt so the cam can't rotate back. It would kind of look like a 1/4 moon shape. They were able to be bought from real racing supply houses at one time. Other wise you may have to get an after market split chain that uses a master link and replace the chain to fix it.

Which bolts are cocked? The ones for the top cam chain guide or the tensioner itself? If it's the tensioner I think you can do all this with it in. If it's the top guide you should be able to fix those because they are in the top cam holder piece and they have to be taken off to get the gear off the cam. Either way it's going to be a lot of work. $$$$

So again is there really a problem? I was going to go into how motors like a V8 with a single carb has unequal length intake runners (center 4 shorter than the ends) and exhaust manifolds/headers of unequal length. So theoretically each cylinder makes a tad different power at a tad different rpm. Which is not noticeable to the driver. But why?

So it might just be better to leave well enough alone as long as its running good. Just a thought.

 

The bike feels just fine... The power is where is should be and it idles without an issue. There are only two problems with the bike; from 5k to 7k it loses a bit of power, but before and after are fine. It feels like a hesitation, which is probably a carb issue. Also, when cruising around in first gear (traffic) when I grab the clutch it almost wants to die out. It will also do this if I have the RPMs high and close the throttle.

From what the mechanic told me, it is the bolts on the cam tensioner.

Thanks again for all the info...

 

I just talked to the mechanic and he is just going to line both the front and back to top dead center and call it done. He is going to put it back together today, so hopefully it will go smooth.