Jump to content

FCR leak jet size/duration


Recommended Posts

A while ago I saw a listing of leak jet size to fuel squirt duration. I have been teating my leak jet duration and found that .40 - .45 sec. (roughly) works well on my 2003 WR 250F. My question is, what size leak jet does that relate to. I did purchase a #40 and the squirt was ~ .95 sec., bike did not like that much fuel. Any help would be welcome.

JRV

Link to comment
Share on other sites

Duration is not only controlled by the leak jet. It is also controlled by the diaphragm rivet length and the AP chamber volume.

So... a big leak jet and a short rivet will yeild a long duration as will a small leak jet and a long rivet.

Leak jet size also affects the sensitivity of the AP system.

The key is the largest leak jet/longest rivet you can run without having a bog. Timing it is good to get you in the ball park but fine tuning by riding is the only way to get it right for you.

Link to comment
Share on other sites

William1, all that is true and you have been doing this much longer than I have. I have had this bike about 4 yrs and have been reading on Thumper Talk about that long. You and a hand full of others are VERY helpful. Thanks.

What I have done on this bike is adjusted the AP squirt to just miss the slide, and using different materials (small guage wire in the leak jet) adjusted the duration of the squirt until the bike responded well during ridding. ( all else with the AP is stock, diaphram, rivit and all. have not done Oring, Doc mod or anything else.) After reading many treads about #40 leak jet I tried one and it was too small creating a rich hesitation (kind of like the large leak jet bog but fuel rich not lean cut out) To test why these 2 LJ's were different I went to timing the squirt. I have my original #90-modified leak jet back in and all is well. Did a trip to Hatfield-Macoy trails last week and no problems. I would like to have an unmodified leak jet in the bowl and that is why I am trying to find the correct size that has the same duration as my modified LJ.

Sorry for the long wind but figured you would understand all I am talking about.

Link to comment
Share on other sites

That chart would be of interest to me as well but, like William said other variables!

I would start with how far is the pump rod sticking out the bottom of the carb body, I set them at 1mm. Next would be pump duration. On 250s I like to adjust it with the leak, my prefference is a long travel/short post diaphram and a leak around the 60 range. Big bikes I want the squirt volume bigger so I go no leak and limit the pump travel

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

×
×
  • Create New...