bad / low compression issue

[Paul-B4]

My bandit 400 was running sweet as a nut and then the starter motor stopped working.

Since changing this small part the bike has run like shit and will not idle. So either its a very odd coincidence that the bike now runs like shit or its something I have done when I replaced the starter motor.

its important to stress the bike literally went from running very well to running like shit in the space of 1 hours time while I put on the new starer motor.

The mechanic has just told me the bike has bad compression on 3 cylinders. He wants to start looking inside the engine for possible causes but before I give the go ahead I want to ask here if there is anything I could of missed?

To replace the SM I removed the carbs and also the cam chain adjustment, could this of caused the issue?

[tomacGTi]

To replace the SM I removed the carbs and also the cam chain adjustment, could this of caused the issue?

Unless you made damn sure that both cams and crankshaft marks lined up when you did this, this could very well be your problem.

Your mechanic will have to make sure the valves didn't smash pistons or break rockers after retiming the motor to make sure that it will run or even get a valid compression number.

[interfuse]

I'm a little stumped... why did you remove the carbs and the cam chain tensioner to replace the starter? The starter is held down by two bolts. You have to loosen an oil line to get at one, but it's a pretty quick and easy. I hope the timing is just a little off and the internals are okay. Good luck. 

[Paul-B4]

the mechanic says the valves are ok, I have not spoke to him about the cams and crankshaft alignment but If they were out he would of said.

I did not adjust the cam chain just removed the adjustment rod to get to the starter.

why did you remove the carbs and the cam chain tensioner to replace the starter?

because I could not get a spanner or socket of the second bolt.

[Chris H]

Just removing the tensioner should not affect the timing. Did you do the work and after take it to a mech because of the bad running? Does he know his stuff and has he given you readings for the comp test he's done?

[Paul-B4]

Did you do the work and after take it to a mech because of the bad running?

Yes

Does he know his stuff and has he given you readings for the comp test he's done?

Yes I have not see him yet only spoke to him on the phone so no readings.


I am thinking its the cam chain or.. starter motor sticking.

[Chris H]

I cannot see how it ran ok before then not so after if the comp was bad- i'd take a look at the starter and more likely the carbs. If for example youve not fitted the vacuum pipe correctly it will run as if one cylinder is bad due to vacuum leak.

[interfuse]

I'm guessing your cam chain has jumped some teeth.

Read this thread, it sounds familiar:

http://forums.banditalley.net/index.php?topic=244.0

[Paul-B4]

Yes I will check this,
If the cam chain has jumped would that explain the bad compression?


 and is this an easy job to fix?

[interfuse]

Yes, if the valve timing is off, you'll have low compression on all cylinders. If nothing is damaged, then it should be an easy fix.