High idle with long offset intake

[Hello Moto!]

So I was tinkering with my bike while trying something for another thread I am currently discussing improving torque and various mods/upgrades. I made a nice discovery that I thought I would share.

I've always ran a long offset intake on my bike cuz for the longest time I was using an hp dellorto knock off and it wouldn't fit with the original intake. After struggling with that carb for a couple years I've since went back to the stock NT carb and have had great results. I just never used it lol. The thing is with both the hp and nt I had a consistent problem with having a high idle even with the idle screws nearly all the way out.

Today I put my short stock intake on and when I went to fire my bike up it wouldn't start off the bat. I have a pull start so I pulled it for a while and it would just putter a bit then die. Then it dawned on me...the revelation! I turned the idle screw about halfway in and guess what? It started right up with a near perfect idle!!

Therefore I conclude that the longer intake was giving me this issue all this time lol. I put the short intake on and no more high idle issues whatsoever. The idle screw is actually responsive to minor adjustments and is in a normal position..no longer unscrewed nearly all the way still having a high idle.

I felt this was important enough to share for anyone looking up this specific or similar issue. It worked for me and I did it by chance. Sometimes going back to the basics can teach you the simple solutions.

✌

 

[Hello Moto!]

Well FML! This must have been a fluke. I just rode to my local post office and on the way there it died at my second stop sign about 6 blocks from my house.

I now have the total opposite effect happening LMFAO. The idle screw has to be all the way in to keep it running. This is crazy s**t man.

So I have a .66 jet in.. It's a little choppy here and there but opens up good and reaches around 30mph. So what's the deal with the idle I wonder? Do I have a leak at the manifold/cylinder seal or do I need to try a slightly smaller or bigger jet. It's my understanding that a jet won't change at idle but WOT.

I know! Maybe I need to set the needle a little richer by a clip or two..or is it leaner Hell if I know but I'll figure it out one way or the other. Because I've got to Mr.!

Anyways there's gotta be an achievable happy medium. I'll try again later.

 

[JerboaJohn]

look at the intake flange. is it the steel one? those don't deal as good as aluminum sometimes the weld is rough. sounds like you might have a leak there, usually it'd make high idle. you can file it then sand it flat. wouldn't hurt anything.
if you can't fix it, do you have other jets? bandaid remedy go richer jet

 

[Hello Moto!]

look at the intake flange. is it the steel one? those don't deal as good as aluminum sometimes the weld is rough. sounds like you might have a leak there, usually it'd make high idle. you can file it then sand it flat. wouldn't hurt anything.
if you can't fix it, do you have other jets? bandaid remedy go richer jet

So I switched back to the long offset and had the problem where I'd have to turn the idle screw in all the way. What I did was put my old hp dellorto knock off back on after I modified it a bit. I took the slide out and successfully removed 1mm of material from the bottom while keeping the same angle slope. My god this was a success! Normality in idle and idle screw responsiveness.

I have it jetted at .65mm which might be a little lean but very responsive. I haven't got a chance to take it for a ride yet but I'm hopeful.