I bought a Ty175 a few months ago, it felt very underpowered so after checking I took it for a re-bore, it turns out it wasnt a 175 but a 125. I took it back to the dealers where i bought it and they were great, it took a couple of weeks but they got me a 175 barrel and head, and had it re-bored for me.

Now i've put it all back together it just not running right. It doesnt want to rev in gear and its not to keen on revving out of gear, the carb was set up for a 125 so i've changed the main jet back to 175 size (240), the only way i can get it to rev somewhere near what it should is to remove the air filter and even the air filter box lid, putting either back seems to restrict it.

Any idea what the problem is or can anyone make any suggestions.

Scott.

Scott, 240 seems an awfull big main jet to me, may be wrong? Removing the air box is letting more air in and leaning the mix up so it revs better, sounds like to much fuel

Edited December 2, 200619 yr by Betarev3

Hi, 240 is the std size according to my Haynes manual - try the ingnition timing, made a vast difference to mine.

YES I AGREE, IGNITION TIMINIG VERY VERY IMPORTANT,NEEDS TO BE BANG ON ASWELL.

Hi,just to add to your checks,check position of jet needle clip for a start try clip position 4 counting from the top,check the float bowl level,float bowl height should be 21mm+or-2.5mmm measured from the top of the float to the float chamber gasket seat (gasket removed).PS if the foat needle is damaged it wont make any difference because it will just over fill and give you an incorrect mixture.

Regards Andy.

Thanks everyone.

Andy are you sure those measurements are right? 21mm from the top of the float, the float itself is about 20-25mm in dia it would have to be sitting on the bottom of the float bowl to give me a 21mm gap.

Scott.

Hi,its correct,should have said to turn carb upside down when measuring,its not the gap between the needle and float that you measure.if this still does not make any sense I will try an scan a copy of how its checked and send it to you.(tomorrow)

Regards Andy.

dude the problem is that somewhere in the airbox or on the airbox cover there is a rubber piece that restricts the airflow, which is right for the 125, but when you have the bigger bore it needs more air so you take it out! Found that out when i was at a classic trial and to make the bike breath better we took the cover off a 239cc ty and put it onto the 125 i was riding and it just bogged down when i revved it! but being idiots we didnt take the other cover and ended up using a bit of cardboard folded up to block the cover!!! the 175's up dont have the little air restricter/different cover but because its a 125 that you have its gonna have the air flow restriction thingy so you need to take it out or change it.

right i hope you understood that and hope it helps