friggin gearbox

[TonyB]

Gees I'm mad with myself ( or I'm plain mad), I had a nice IT465 but allways hankered for a yz465 so I changed everything to yz including what i thought were the different gears, but its all gone back together and took it to qvmx weekend and the damn thing hunts between 2nd and 3rd??? I replaced all gears to yz gears (nice 1st and lower 5th) so in effect i now have
1st pinion -yz
1st wheel - yz
2nd pinion - it
2nd wheel - yz (because it hase 3 dogs behind to mate with yz 5th wheel)
3rd pinion - it
3rd wheel - it
4th pinion -it
4th wheel - it
5th pinion - yz
5th pinion - yz

if there is a gearbox doctor in the house i would appreciate some help..I wonder what other gears needed to be replaced? 

[Nathan S]

2nd pinion - it
2nd wheel - yz (because it hase 3 dogs behind to mate with yz 5th wheel)

My own inability to get a YZ125D gearbox to stay in 1st gear rules me out as an form of gearbox guru, but the mix-and-match 2nd gear is a worry...

Ahhh... let me troll some part numbers and I'll see if I can come up with something more useful than the page of "It's possible", "maybe", "you might find" that I was about to type...

Edit: I see your dilemma... For anyone else reading, the 2nd and 3rd gear pinion part numbers are the same YZ ~ IT, but everything else is different.

Based on the part numbers, it sounds like the problem is with the assembly/clearances, rather than incompatible parts.
Everyone says that you should replace gears as a pair, so (in the absence of anyone who actually knows what they're talking about) I'd be looking at fitting a the 2nd gear pinion from the same source as your 2nd gear wheel.

And totally unrelated to your actual problem, what's the change from 4th to 5th like? Small? My parts lists don't show the tooth counts (they do for the earlier bikes), but logic and the part numbers both suggest that a YZ would have a closer 3rd to 4th change, as well as bringing 5th lower...

[wesley]

TonyB ........whats the number 2 shift fork like,,i have had dramas in the past,but sounds to me is the miss matched second gear set,,,,,if all fails i have a complete yz465H gear set in excellent condition.....

[TonyB]

Thanks guys, I pulled it apart last night and there is a difference in the primary shaft which first gear is part of. The first gear is narrower and so 4th which clips on next to it is too far from the dogs of the next controlling gear, only 2.5mm dog intersection occurs so it just jumps off 4th ( I thought it was jumping out of 3rd? so i have now gone back to the IT1st (complete primary shaft) and left the yz 5th in. I much prefer the lower yz 5th as the motor would bog and lose the band in thick sand or mud and I would have to go back to 4th again. I hope now that the closer step to 5th will keep me in the meat of the band.

[vandy010]

hey Tony,
i'd imagine 1st gear on a 465 would only be used in the pits anyway, no biggie!
so how was the new qvmx riding area? wet?
hope your g/box works this time round.

[TonyB]

Hi Mike, yes the weekend was excellent, track was great but i did'nt get much action cos of the gearbox, but all who were there enjoyed it immensly. The dam and movies was a nice addition too. I recon it should be on the qvmx calender for a familly weekend every year. A one day race would be too far for the majority of us but a weekend is just right. I hope to have the bike running for the BMCC sign on day, and maybe I will see you there?