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Vibration issues

Posted: Fri Apr 15, 2011 6:47 pm
by Boertjie
Naand se al die Ooms! (Evening all the Uncles!),

I did some work on the top end (R100S 77), new piston rings and replace all the gaskets and surprisingly after the 3rd tickle of the starter the engine start and oil pressure etc. were OK.
I went for a couple of short rides and noticed vibrations that I can feel through the handlebars and even the mirrors were vibrating so that I can not see in them. Thus far I have checked the timing and did some adjusting to the carbs but the vibrating is still there. The engine sounds very solid thus far, and power are plenty.

The higher compression also make the bike now harder to start, and every time it sounds as if the battery is about to quit. Battery is new and fully charged.
Thus far I have done 100km's and no other issues except the vibrating.
Now are the rings still manage to "find" themselves in the cylinders and should I just ride the bike until all settles down or are there some other things I need to attend to or look at?

Thanks

Regards
Johan

Re: Vibration issues

Posted: Fri Apr 15, 2011 7:45 pm
by Deleted User 72
Have you checked that both throttle cables have equal slack? I find this test best done with a manometer @ mid rpm.

Re: Vibration issues

Posted: Fri Apr 15, 2011 9:39 pm
by Motorhead
How high is the compression?

as the starter is almost at the limit with a stock motor

Re: Vibration issues

Posted: Sat Apr 16, 2011 12:30 am
by Chuey
I think that sometimes, when the starter is having a hard time it is the timing. If so, someone who knows more than me, and that's almost everybody here, will say if that's a possibility.

Chuey

Re: Vibration issues

Posted: Sat Apr 16, 2011 2:16 am
by Boertjie
Thanks, yes I will have to look at the timing again, my 4$ balancer also show the carbs are OK and the slack are even on both sides cables. I see there was similar topic from Tim a while ago, but could not pick up something there as well. I got me one of those ultrasonic laser Thermometer's a while ago and interestingly the one cylinder seems to be 7-10 degrees Celsius higher than than the other.

Regards
Johan

Re: Vibration issues

Posted: Sat Apr 16, 2011 8:36 am
by bbelk
Boertjie wrote:Thanks, yes I will have to look at the timing again, my 4$ balancer also show the carbs are OK and the slack are even on both sides cables. I see there was similar topic from Tim a while ago, but could not pick up something there as well. I got me one of those ultrasonic laser Thermometer's a while ago and interestingly the one cylinder seems to be 7-10 degrees Celsius higher than than the other.

Regards
Johan
Being even slightly down wind from any moving air (the side away from the door) seems to make a difference in the temperatures. I have never confirmed this by measurement, but it feels that way to me.

Also, the hot side may be running leaner than the cool side.

Re: Vibration issues

Posted: Sat Apr 16, 2011 11:00 am
by Deleted User 62
I agree with bbelk, try adjusting the carbs on the hot side slightly richer. I will give this a try on mine this pm.

Re: Vibration issues

Posted: Sat Apr 16, 2011 12:29 pm
by Boertjie
Thanks Bbelk and Tim, I've been fiddling with the carbs, problem is I cannot go for a ride due to rainy weather and now the one side is 160 Degrees Celsius to the 140 of the other side. I'm working in the garage. Time to get a fan on the bike I suppose..

Re: Vibration issues

Posted: Sat Apr 16, 2011 9:09 pm
by Deleted User 62
Yes, use a fan! My Plan: to rev my /5 to the point of vibration while on the stand, and lock the throttle there so I could fiddle with the carb to see if it makes a difference. Shoot, I'm going to try that right now, and I'll get back to you. Another thought, if you installed new head gaskets, they will tend to settle in for the first few miles and close the valve clearance. Have you rechecked your valve clearances? I'm thinking there's a possibility hard starting might be too tight valves?

Re: Vibration issues

Posted: Sun Apr 17, 2011 7:44 am
by Boertjie
OK, left side exhaust valve clearance was too tight, will get back to give update.