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What's wrong with my engine
Posted: Mon Nov 21, 2016 6:00 am
by droy
Hi all,
I have a 1970 450cc Scrambler that's recently started making strange sounds. It still starts and runs, but makes a grinding noise every few seconds and I feel a loss of power and hesitation along with this noise. Can anyone give me an idea of what is going on?
I couldn't upload a video on this forum but if you can give me your email I'll send it.
Thanks
Re: What's wrong with my engine
Posted: Tue Nov 22, 2016 2:46 pm
by BevHevSteve
what have you checked thus far?
Re: What's wrong with my engine
Posted: Tue Nov 22, 2016 3:15 pm
by droy
A new spark plug, fresh gas. Can't think of anything else.
Re: What's wrong with my engine
Posted: Tue Nov 22, 2016 4:40 pm
by BevHevSteve
"makes strange sounds" and "makes grinding noises"...............
it could be literally anything that is a moving part. Crap stuck in the tire and rubbing on the frame, a loose sprocket or clutch basket nut, semi frozen piston or valve............ etc etc,.
I'd start looking at everything, then fire it up and listen with a stethoscope to find where the noises are coming from. Then start taking things apart to define the problem and fix it.
Re: What's wrong with my engine
Posted: Thu Nov 24, 2016 4:12 pm
by ducadini
Droy,
got the movie, tried to slow it down but my computerskills let me down ;-)
Engine at about 1500 rpm, so clutch at about 600 rpm or 10/sec.
The noise is repititive at about 3 seconds .
So it probably isn't one of the clutchbearings, since the clutchassembly is spinning WITH the ingoing shaft and the bearing isn't turning.
Could be that two teeth on the primary crankgear are damaged AND two on the clutchdrum and it takes a few seconds until "they meet again".
Could be that the bearing of the ingoing shaft has "lost its marbles", and they are turning around , rubbing against eachother and frequently slowing down the shaft, hence the grinding noise.
Take a big screwdriver ( the tool ! ) and a set of protective headphones, put the screwdriver to "a" place on the crankcase and them put your headphone against the handle of the screwdriver. You eliminate the engine-noise and get a better sence of were the noise is originating.
If You have access to a stethoscope (best with a extension-rod) this is also working.
Check a few spots, You will hear a difference as you get closer to the source.
Enjoy ;-)
ciao
ducadini