Page 1 of 2
RB20 problem
Posted: Tue Mar 01, 2016 11:24 pm
by kevspeed
Hi all,I'm helping a mate out with his RB20 kitted scoot,the problem is,it feels very low on compression.
I can almost spin the flywheel by hand with the plug in!
I can't say how many miles its done,but its been on the road for just over a year.
What I'm after is the maximum piston to bore clerance and the maximum ring gap so I can check the kit for excessive wear.
Thanks in advance...........Kev
Re: RB20 problem
Posted: Tue Mar 01, 2016 11:32 pm
by coaster
Why not try a compression tester before you tear it down? What does it run like anyway?
Re: RB20 problem
Posted: Wed Mar 02, 2016 1:51 pm
by kevspeed
Its showing 6kg/cm on the compression tester,what should it be?
Re: RB20 problem
Posted: Wed Mar 02, 2016 3:28 pm
by dave411
Hi Kev,thats only 85lb psi,a bit low dont you think?
Re: RB20 problem
Posted: Wed Mar 02, 2016 4:09 pm
by kevspeed
No idea,never done it before,so I've no max/min figure to work on!,I'll just strip it down and measure the clearances if I can get a max/min for them!
Re: RB20 problem
Posted: Wed Mar 02, 2016 6:49 pm
by Grumpy225
Typically you want to see at least 100psi just to make smoke.
On an RB20 I'd think it should be closer to 135psi or so depending on the head.
I bet a $1 you have a stuck top ring in the piston. :d
Re: RB20 problem
Posted: Wed Mar 02, 2016 7:37 pm
by kevspeed
My thoughts exactly,I'll be in it tomorrow, hopefully a gummed in ring or two!
Re: RB20 problem
Posted: Wed Mar 02, 2016 9:59 pm
by sydduckett
kevspeed wrote:My thoughts exactly,I'll be in it tomorrow, hopefully a gummed in ring or two!
Id be hoping jts an air leak and not a stuck piston.......
Re: RB20 problem
Posted: Wed Mar 02, 2016 11:06 pm
by kevspeed
Either or,as long as the bore isn't damaged
Re: RB20 problem
Posted: Wed Mar 02, 2016 11:55 pm
by Markpm
0.6 mm is maximum ring gap