background.
I have just got a 1975 T500. i have cleaned the carbs changed the g box oil, new condensers and points, also new petrol / gas.
it starts runs a bit lumpy i have checked the timing with a strope and its spot on.
when i turn the tick over down to 1250 ish it starts to sound a bit rumbley down in the crank area.
the questions
what is the correct tickover rpm?
at this RPM are these bikes known to make a rattle/rumble noise
Are you talking rumble or rattle? If the clutch has excessive end float it rattles quite badly. Once you shorten the bush it runs on that noise goes away. The bottom ends of the T500 are pretty solid.
If you pull the clutch lever in and the noise goes away or lessens considerably then its probably as Fritz says "excessive end float in the clutch". They do rumble a bit in the lower end with age, not the quietest of motors.
1968 Cobra T500. Now that I have quietened the cyclinder rattle (0.5 o/s rebore - nice result) the clutch rattle really bothers me. The bike has a genuine 10k miles on the clock so it ain't axial float. I stripped the clutch side to find a lot of radial movement on the helical driven gear against the basket. This is the part that's riveted together. I am pretty sure that's the source of the noise. (and it quietens when the clutch is pulled in, but not entirely).
Manual says don't disassemble but heck, you can order new rivets from Robinsons Foundry. They drill our real easy. Inside there are 8 X 4cm dougnuts
which locate in 8 round holes. They seem to have shrunk over the 40+ years that the bike has been idle. About 0.5 - 1mm clearance across the diameter. The gear rotates (rattles) freely around 2-3mm.
Not sure if you can find new rubbers now. Paul Miller is advertising a NOS basket but it may be as old as mine.
Has anyone repaired these? I am considering a RTV silicon fix. I will report back if it works.
There was a post that showed the process of checking and adjusting the end play on the 500 clutches and it involved the bearing ( spacer ) that the clutch rides on #17 http://www.oldjapanesebikes.com/mraxl_G ... index.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;..... Page 41..... , if the #17 is just a bit too long it will allow the clutch basket to float back n forth . I believe the writer wet stoned the end of the #17 piece till the end float was within specs .
I once adjusted bushing too far per Suz. I had the noise when clutch engaged idling rattled loudly.
Last winter I rebuilt that motor (t350) and ordered a new clutch bushing/spacer. The new one came with washer attached too (see you don't use the one against engine case side).
Now, the clutch is just as quite engaged as it is disengaged. I see it is still avail for t500. Maybe Suz improved design/tolerance or i just got lucky.
If was going to pull clutch a part i would order that $13.00 item new again.
parksie wrote:If you pull the clutch lever in and the noise goes away or lessens considerably then its probably as Fritz says "excessive end float in the clutch". They do rumble a bit in the lower end with age, not the quietest of motors.
I rebuilt my engine from the crank up last summer and now I am, getting rumble in neutral and it goes away when I holdl the clutch. Is the only way to fix this to rebuild the clutch? It works normally otherwise.
Look here http://www.ozebook.com/compendium/techbuls/index.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
in section 10 to 18 no.15
Note this is only for the twins, triples may be different
A RESULT! Having opened up the clutch on my Cobra I packed the gaps around the rubber doughnuts with engineers silicone (soft setting) and had the thing professionally rivetted together. The play (around the circumference) has gone and as it's silicone there is some give under load.
Did find that the primary drive pinion was not super tight on the c/shaft and believe that combination of play here plus clucth basket gave the LOUD rumble. I renewed the key and torqued it snugly.
Hey presto! Super quiet clutch at any RPM with next to no difference with the lever in or out.
A mate told me you can get clutch doughnuts for a number of bikes that look very similar in profile. Mostly off road, eg KTM. It may be that they fit. But for now I am just fine with my super-quiet engine.
