T500 Jetting

Phil C · Post by **Phil C** » Fri Jul 31, 2009 2:26 pm

Can anyone tell me if the T500 needs the large 150 main jet with the short intake stubs. There seems to be such a huge difference between the 97.5 jets and the 150s and I was wondering if it was due to the intake stub length.

Phil C

TLRam1 · Post by **TLRam1** » Fri Jul 31, 2009 4:24 pm

The early T500 had larger jets due to different cylinders/porting, not too sure how the length of intakes will affect that.

What year is yours?

Phil C · Post by **Phil C** » Sat Aug 01, 2009 12:39 am

Thanks for the reply Terry,

I have a 74 T500L but with later cylinders. I have spoken to a couple of established 2-stroke tuning guys in the Uk and they tell me that such a big difference in the main jets cannot be attributed to small changes in the porting. They said that porting normally required changes of two or three sizes bigger at most. They said that running pods or bigger carbs would have the biggest effect. I am running a stock airbox but with the short stubs. I am trying to find out if the T500 with the short stubs always need the 150 main jet and the longer stubs need the 97.5s. Some reading I have been doing also suggests that the intake length to the carb will affect the main jet size considerabley because of the position of the carb in the intake velocity wave.

I have some mild porting and chambers but power is down 50%.

Phil C

argo1974 · Post by **argo1974** » Sun Aug 02, 2009 2:59 am

Mikuni made 3 types of different main jets so plain numbers are not representative.
http://www.mikuni.com/pdf/vmmanual.pdf
http://www.ozebook.com/compendium/t500_files/mikuni.pdf

Phil C · Post by **Phil C** » Sun Aug 02, 2009 5:55 am

Ok, I see now that the 150 Amalstyle jet is about a 112 in the 'button style N104 type.

Thanks for clearin this up.

Phil C