Apump mod: Does the '07 and later still need it?

Some FCR carbs (Honda, Suzuki) come with an upgraded Accelerator pump system, that does not need the O-ring or Merge racing linkgage spring upgrade.

Does the 2007 still need the Apump upgrade mods, or does it have a newer FCR version carb?

Some FCR carbs (Honda, Suzuki) come with an upgraded Accelerator pump system, that does not need the O-ring or Merge racing linkgage spring upgrade.

Does the 2007 still need the Apump upgrade mods, or does it have a newer FCR version carb?

Yes they need the mod. A Merge spring works wonders. Also look at the leak jet. I skipped all the BS and went straight to a 40. Some do 50 etc.

Yes they need the mod. A Merge spring works wonders. Also look at the leak jet. I skipped all the BS and went straight to a 40. Some do 50 etc.

Good. Thanks Coop.

That's what I thought I remembered. I posted this after buying the merge racing spring on line, then thinking, ' wait a minute... '

Removing the carb I discovered a NCSQ needle, 45 pilot, 175 (!) main, and 45 leak jet. Un corked in/out. 3 year old gas had stuck the float needle, but a little Brasso and a Dremel fixed that.

When I got it running, that old familiar 'vauge throttle' was there, and I figured it was the apump linkage spring.

Only Hondas made after 2006 have a push intead of a pull linkage. I assume there is some agreement made between Keihin and Honda that prevents the others from using it.

After you do the spring (or oring or wire the linkage), check/reset the AP timing per the manual. You want to ensure it is correct (or at least close) before you do the fine adjusting.

The basic rule of leak jet is the larger the bore, the smaller the jet.

Only Hondas made after 2006 have a push intead of a pull linkage. I assume there is some agreement made between Keihin and Honda that prevents the others from using it.

After you do the spring (or oring or wire the linkage), check/reset the AP timing per the manual. You want to ensure it is correct (or at least close) before you do the fine adjusting.

The basic rule of leak jet is the larger the bore, the smaller the jet.

Yup. I follow your posts, Coop's posts, and Eddie's posts about the trials and tribulations of the FCR pumper.

The basic rule of leak jet is the larger the bore, the smaller the jet.

Not entirely true. The larger the bore the more fuel is allowed back into the float bowl and in turn less fuel making it to the motor through the accelerator pump.

John

JD, you misundertood me. The larger the bore (125, 250, 450, 510, 600, 650), the smaller the leak jet.

AHA! That sounds exactly why I have so much trouble with low speed throttle control!

It really messes with my balance in muddy conditions, between that and the engine braking. Would someone direct me to the best post on the subject?

AHA! That sounds exactly why I have so much trouble with low speed throttle control!

It really messes with my balance in muddy conditions, between that and the engine braking. Would someone direct me to the best post on the subject?

Just buy a Merge Racing Apump linkage return spring (detent spring) and install it. Problem solved.

You might have to re-address the pump timing after wards, assuming it's in adjustment now.......

Bill, did you pick up another Yamaha?

Bill, did you pick up another Yamaha?

Yes sir! Motorcycles are just falling out of the sky, over here.

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