Cafe Racer Forum banner

New carbs on 175

1669 Views 17 Replies 4 Participants Last post by  bfd
Yesterday I fired up the 175 with the 24mm Keihins and WOW, what a difference. My driveway is too short to ride it on and the hay field was pretty wet so my testing consisted of calling my buddy Joe so he could hear it run over the phone.
Hawk school tomorrow will be a good shakeout.
Right now I have the 100 main jets and needles 2nd clip up from the bottom. Didn't get the airscrew adjusted at all- just 1 turn out from the bottom.
Scott/JohnnyB what are you guys running?

1 - 5 of 18 Posts

You'll find the bike really comes alive at about 7,000- 7,500 rpm. Also become very easy to get the front end up on starts. Sometimes during the first to second gear change too.

I always start with 100 mains and needle in the center. Sometimes you have to raise the needle a notch to get rid of a dead spot right around 7,000. 120 main jet is going to be way rich. The bike will tolerate a way rich condition don't let it fool you into thinking it's running the best...dyno tests show the power starts dropping off real quick when it's too rich but it will often sound/feel fine.

That said...I've never run one with OEM 120 never know how they flow compared to new/aftermarket 100 mains...only way to know for sure is to do some plug runs.
Hiroshi's bike should be there along with Hiroshi.

I expect you guys to help him with any tuning changes should the bike need them. It looked a bit rich to me when I delivered it...better rich for breakin than lean.
You guys know these bikes so keep an eye on his for any of the typical problems.

He's got the PE24's with 102 mains and middle position on the needle. About 45 degrees advance, 15/38 gearing. Check out the belly pan if you get a chance.
All the dyno work I've done has shown 45 to 50 degrees. 50 is good for peak hp but hurts you in mid range..45 to 47 works good on my bikes.
If you guys are talking K&N filters I found this place called Martel Racing...they basically drop ship from K&N, you can order any filter that K&N carries. That's where I got the nice tapered filters for Hiroshi's bike and some for Mary's old school Keihins.
Might be more expensive the Kirk though...Martel seems to get MSRP for them.
Don't use the oil, it will restrict air flow.
I basically just use them to keep sand and debri out of the carb. The chances of a race engine lasting long enough for super fine particles to wear it out is pretty much nil.
I also like filters because they create a nice stable dead air space outside the carb inlet...much better than a buffeting wind on the straight at 80 mph.
1 - 5 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.