OzVMX Forum

Marque Remarks => Yamaha => Topic started by: ola_martin on August 13, 2010, 09:47:48 pm

Title: XT/TT jetting
Post by: ola_martin on August 13, 2010, 09:47:48 pm

Can anyone help me with a startingpoint on the jetting of my SR500 engine? Stock engine with 36 Mikuni carb.
Thanks.

Title: Re: XT/TT jetting
Post by: brent j on August 13, 2010, 10:24:36 pm

Try this
Main                        230
Pilot                         35
Slide                        2.5
needle                      6F9
Needle jet                 156 series  P-6
The 156 series needle jet is for four strokes (supposedly) and it pays to use a jet extender between it and the main jet as the needle can block the main in the fully closed position and you will chase jetting forever.

I'll try and find the link to a site which lists quite a few different set-ups people are running

Title: Re: XT/TT jetting
Post by: ola_martin on August 13, 2010, 11:16:59 pm

Thanks, great!! ;D

Title: Re: XT/TT jetting
Post by: curly001 on August 14, 2010, 05:12:46 pm

I'm running the following set up on my XT with predator 34mm Exhaust and K&N filter
main 230
pilot 35
slide 2.5
needle 6FJ4/7
jet needle P2 (188)

The P2 (188) is used on 4 stroke suzuki motors.
The link for the different setups is in the SR forum.
Curly

Title: Re: XT/TT jetting
Post by: ola_martin on August 16, 2010, 05:41:10 pm

Thanks again, just fount that the carb I had didn't have a idle screw, so I'll have to find another one... :(

Title: Re: XT/TT jetting
Post by: ola_martin on September 20, 2010, 10:18:02 pm

I found a 38 Mikuni, do you think this will work on a SR500 with a straight through exhaust ? If not will it work if I make it 540 hi-comp and flow the head also?

Title: Re: XT/TT jetting
Post by: Colin Jay on September 22, 2010, 10:21:58 pm

I run 38mm VM Mikunis on two of my 500 engines.

One is a SR500 engine, 500cc, 12.5:1 CR, flowed head WEB 88A cam Straight thru megaphone exhaust, run on 125 octane unlead race fuel.
Jetting is;
270 main
6F9 needle on 2nd clip
P6 needle jet
#2 slide
20 pilot

dynoed at 43HP

XT500 engine, 535cc, 10:1 CR, flowed SR head, TIGHE 503 cam and a fairly free flowing exhaust, run on BP Ultimate;
190 main
6F9 needle on bottom clip
P6 needle jet
#2 slide (needs a 1.5)
25 pilot

dynoed at 30HP

CJ

Title: Re: XT/TT jetting
Post by: ola_martin on September 23, 2010, 05:19:32 pm

Thanks a lot, that's great! ;D ;D