Pit Bike Club

mito350 · 03-06-2006, 05:33 PM

See if anyone can help me out, I recently had to replace the gearbox in my bike due to 3rd gear smashing, I got a good con second hand one from a known working bike. Its all in and running fine in everygear aprt from 3rd, what happens is it feels like its jumping out of gear then back in, out, in etc, Ive had it all stripped down and the cogs appear to be fine, everything seems to be put i right aswell!!

Has anyone had this problem and what did you do to fix it?

Cheers

LEEROY_UK · 03-06-2006, 08:28 PM

Take a read of this .It is very common with the 110/120 thumpstars.
Hope it can help you out.

[QUOTE]
I have now come up with a fix for the THUMPSTAR gearbox smashing problem.

I intend getting in contact with the guys selling the THUMPSTAR and telling them about it too.

Basically the thumps are smashing 3rd and 4th gear if you land short and dont pull the clutch in on landing...this in my opinion is fundementally down the quality of the casting of the chinese gears that are used.

Thus the mod involves re-fitting the gearbox with a pukka HONDA gearbox.

Over the last couple of days i have altered Danny Massey's Thump to incorporate a HONDA 3-speed gear box and still keep all of the thump cases and clutch mechanism.

It involves getting the HONDA layshafts centre ground down to 12mm so that they then fit into the smaller bearings in the thumps case. You then need to flat spot a small recess in the primary drive gear to allow the C clip to fit and Bada Bing - one thumpstar engine running HONDA 3 speed box - better quality gears and you can still run all of the cylinder head barrel clutch and kickstart as before - so you have a 120cc - 3 speed honda - which should NOT break.

it take a day to fit the box as you will have to strip your down and then put the NEW one in - but in my opinon - i would do it before i blew the standard one up - but i will leave that up to you lot to decide.

Geof