Tuning hobbit w/ 15.15 SHA

I am not seeing many comparable builds to mine to base my initial jetting and timing off... I have a little PTSD from my last attempt at this kit and want to make sure I'm not chasing the right tune by over-lean conditions.

I have a hobbit w/ DR 70cc cylinder, 46mm head, proma circuit, mlm 15 sha intake, 15.15 dellorto sha.

Stock transmission as far as I know and stock reeds...

Does anyone have a similar build and recommendations for timing/jetting? I have my timing slightly retarded and I'm assuming 70-80 jet range.

Re: Tuning hobbit w/ 15.15 SHA

Start rich and bring it down until the four stroking stops.

I used the stock kehlin on mine. Thing rips.

Re: Tuning hobbit w/ 15.15 SHA

Jason White /

I see a lot of people using that carb. I'm so used to swapping out stock carbs as a necessity for some of my other bikes, I didn't even think about re-using the kehlin

Re: Tuning hobbit w/ 15.15 SHA

Totally normal JBOT /

Remember, since it sounds like you haven't done any trans work.

A poorly tuned tranny can make your bike seem like it has a carb issue.

You must do transmission work if you want to run a hobbit to even 50% of its potential.

This means popping open the rear pulley and cleaning up the metal slides with a dremel, then regrease and maybe add a stronger spring,

And swapping rollers up front to correspond to the rpm range where the bike/pipe makes the most power..

But as far as jetting yeah just pull the rollers out and ride it with no variation and that will give you a good idea. Use a temp gauge and if it's running decent and not too hot start tuning the trans.

Re: Tuning hobbit w/ 15.15 SHA

Never thought about leaving the weights out before tuning the transmission. I feel like even if the jetting is dead on it would run hot without the variation. High rpms and low speed.

Re: Tuning hobbit w/ 15.15 SHA

Totally normal JBOT /

Nope. You don't go ripping at max for hours, just a slow tune.

It's a great place to start tuning a variated bike..

If you can't clear the jetting with no variation you're too rich.

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account