Gg250 Pro Tuning

[laser1]

I had a slight pinging issue when I was running 75/25 in my old bike - so went to 50/50. This bike would probably be OK.

[laser1]

Spent a couple of hours testing pilot jets today in hot weather and familiar sections. The slow, tight uphill sections really help resolve any question regarding one jet over another. Smaller pilots = smoother power, and less of it. the #35 felt like I was riding a 200!

Original pilot was the best for me. Changed it back.

My buddies 250 (same gearing as mine) with a Keihin is smoother off the bottom, better feel and has just about as much power as my bike on the pilot - more everywhere else. Has very good over rev as expected. (the over rev isnt a goal for me other than just playing around) Im going to try the VHST next rather than any slide work.

[motomerlin]

26mm VHST - ran S32 (or S34) pilot, D37 needle - clip on groove 2 from bottom, 271HE needle jet, 120 or 118 main.

I played with the pilot size & needle clip postions to get best response.

Gave crisp smooth power. (on UK fuel!)

The VHST needs a 300 float jet - otherwise it runs out.

I tuned down the outlet to fit the std GG intake manifold.

Or you need the bigger manifolds as used with Keihin.

I always found the std dellorto too rich at/near idle.

Let me know how you get on,

Cheers, Mike

[laser1]

26mm VHST - ran S32 (or S34) pilot, D37 needle - clip on groove 2 from bottom, 271HE needle jet, 120 or 118 main.

I played with the pilot size & needle clip postions to get best response.

Gave crisp smooth power. (on UK fuel!)

The VHST needs a 300 float jet - otherwise it runs out.

I tuned down the outlet to fit the std GG intake manifold.

Or you need the bigger manifolds as used with Keihin.

I always found the std dellorto too rich at/near idle.

Let me know how you get on,

Cheers, Mike

Thanks for all the info Mike. I'll probably turn down the outlet so I can easily compare to PBHL.

[laser1]

Update:

Switched to a VHST and after trying various jetting combo's, now have the bike running very nice. I find the VHST smoother w/better throttle response way down low (what I was looking for) with smoother/higher over rev. I was happy with the PBHL, but feel the change are worth it as I had access to a "free" VHST. (the cost of the jets, needles and fuel valve was a total of $80)

I really appreciate all the input folks gave me - especially the insight provided by Senior Blanco (Marlintec)