yx 140 gearbox help

[tinxy]

hey guys need a bit of help with my yx140 gearbox bear with me im new to pit bikes but have a good mechanical background so im sure ill get there with your expertise


rite the bike was riding verywell when i bought it but was due a clutch change the only thing i ever noticed was that when coming from low revs in second it felt like it had a hard kick before really powering on

i then changed the clutch and this felt as it was then 2 days ago i was using it and i began getting a terrible noise and the thump before giving me power was alot worse

and after a while it would just disingage and bite as and when it chose so i stoped riding the bike and pulled it apart as i though it must be gearbox related as it only happens in second gear 1st 3rd and 4th are fine even giving them proper stick .

i have no cracks in my casings the gears look mint as do the dogs the only thing i could find was a bit of wear on the selector forks im not 100% this is the problem .

you guys no these bike so hopefull you can tell me were to look or what to look for to solve this as its doin my head in :action-smiley-003:

heres a few pics of my selector

cheers guys J

 

[no_crf50_here]

I can see your problem.. Looks like no oil.. \:beerglass:

 

[sean01]

hmm, easiest way out of this is to replace everything in the gearbox..
iv seen engines that have no real damage at all but yet still miss gears.. tried all sorts of things to correct it (shims, new forks and so on) all with no joy.

changed the entire box with shift drum and selector forks and all was good..

my guess is just the slightest bit of wear on the fork and gear dog causes this problem as then the gear doesnt mesh properly..

 

[TDR-Shitbox]

mate i had the same problemo i had the change the modulator thats about it mate went like a dream after

 

[tinxy]

sorry boss im being a noob but whats a modulator :iamwithstupid:



cheers so far guys its nice to have some real advise

j

 

[DvDRip]

yea what the F@$K is a modulator?

 

[sixeven]

your gearbox is rooted. order a new whole set including a shift fork(which is now bent by the looks of the marks) and then she will be sweet.

 

[sean01]

yep for the price of a complete gearbox its not worth the drama's of stabbing in the dark and reassembling it just to find out its fooked still

 

[tinxy]

im from the uk and can find a decent priced full gearbox what sortof $ you guys pay

 

[sean01]

GEUNINE YX 140CC ENGINE ALL UP GEAR BOX ASSY - eBay Other Makes, Bike Parts, Motorcycle Parts, Accessories, Cars, Bikes, Boats. (end time 23-Jun-10 20:22:59 AEST)
GENUINE YX 140 150 160 CC ENGINE SELECTOR FORK ASSEMBLY - eBay Other Makes, Bike Parts, Motorcycle Parts, Accessories, Cars, Bikes, Boats. (end time 12-Jun-10 17:39:56 AEST)
COMPLETE YX 140 ENGINE GASKET KIT - eBay Other Makes, Bike Parts, Motorcycle Parts, Accessories, Cars, Bikes, Boats. (end time 21-Jun-10 17:06:20 AEST)

thats just a quick find, could probly price bash a little from elsewhere

 

[tinxy]

cheers mate proberly going to order this an i should be good to go again ???

OORacing - performance monkey bike, pit bike, madass, zoomer, dirt bike components - 140cc All up gear box upgrade (Powered by CubeCart)

how long with good oil changes and a clutch gear change should a box last ??? cheers so far james

 

[sean01]

my yx140 was at least 2yrs old before i removed it for a bigger engine. never had a drama with the gearbox..
oil changes were done at least once a month or every 10-15hrs of riding..

and yeah that kit should get you going..

one other thing that hasnt been mentioned yet is a bent gearshit shaft can cause some dram's too..just check it out while you have it apart

 

[tinxy]

ok mate ill have a good look around is there any guide to put a gearbox back togearter as i mite forget somthing haha cheers james