Carburetor and Fuel System
Title: Carb tuning
My 57 has a Keihin butterfly style (not CV) carb. It has a 100 pilot jet and 185 main jet and it is WAY too rich. If I put a brand new set of plugs in it and run it 10 miles (medium to low speed, just puttin') the plugs are black!
I put a 70 pilot jet in it but that seems to be way too lean (coughing and sneezing thru the carb).
So here are my questions:
* There are a lot of jet sizes between 70 and 100, and I don't really want to buy one of every size - how do I hone in on the correct size?
* Where can I get jets and/or a rebuild kit for this carb?
* Does anyone have any good tuning directions for this carb? (Most of the directions I find on the net are either too general or are specifically for the CV).
* Has anyone had any experience with the adjustable mainjet kit that is available for this carb?
I know someone's going to say just put a Super E on it, or put the Linkert back on it. The Super E is not in the cards right now - already way over budget on this project. I s'pose I'd be willing to try a Linkert if I could find a good one for cheap, but I hate to give up the accelerator pump.
Thanks for any thoughts, tips or suggestions.
Post by BillyW on Aug 2, 2004, 9:01pm
Any Linkert in usable shape is worth more than an S&S E. If you find one super cheap, expect to spend $$ to get it restored to operating specs.
Never cared for the Kehin butterfly. but if 100 is way too FAT & 70 is too lean split the diff. Try around 80-85 to start. That is a beginning .
This assuming your air cleaner is in clean usable condition.
Need more info: Is this carb New to your bike ??
Or did it just start doing this ?? Important!!
Post by 57pan on Aug 2, 2004, 10:36pm
Billy,
The bike had a Bendix on it when I first got it, and that carb was running rich. The local shop where I had it worked on put the Keihin on it and those are the jets that were in it, and it has run rich since it was installed last year.
I have done a complete top-end job on it since then and am just now getting it back into running condition and the over-rich condition still exists.
It has a foam air filter element - I'll try cleaning and re-oiling it to see if that has anything to do with it, but that element was cleaned/replaced at the same time the Keihin carb was installed.
Post by BillyW on Aug 3, 2004, 2:03am
I'm NOT surprised that you had to do a Top-end. As an Over-rich condition causes the extra gas to wash the oil off the cylinder walls & thus creates pre-mature bore wear, pistons & etc...
That's the Seriousness of having it properly jetted.
I recently did a Top -End on a Brand New Sporty with ONLY 13,000 miles. It Had a Dyno-Junk kit put in it New, & was terribly Over-rich just washed the oil off & wore out the top-end out.... "TRUE" .....Just out of warranty.
Jetting is crucial in 2 respects:
(1) Too Lean = Overheating/holes in pistons
(2) Too Rich= Premature wear due to gas washing off the oil that protects the parts, bores, pistons & etc...
The Air cleaner I mentioned because, if it's clogged/dirty the motor can't get the deep inhale of air needed for proper fuel/air mix, causing Over-rich condition..
If it's been a Year without washing & re-oiling it.
Do it anyway...It's time..& Good maintenence.....
Try the 80- 85 jet & let us know how it reads. When you change jets, it's best to install new plugs to get a better "READ" off them. When you start it If you can, avoid using the choke as it will color the plugs & give a "False Reading"
Just needs dialed in...
Post by Cotten on Aug 3, 2004, 3:52am
Linkerts don't need an accelerator pump.
They use a nozzle with a built-in reservoir to meter an extra charge of fuel upon the demand of accellerating.
No raw un-atomized fuel, no diaphragms to split, no linkages to get gummy, no tiny orifices to plug up, no waiting for the pump to re-fill.
Post by haggis on Aug 4, 2004, 3:48am
Ah Ha.... were back on the Carbs again!!
Me I love a good Linkert..nothing works like it...the motor was designed to run it...why run anything else?
Give your Pan a Linkert...it;ll love you for it!! ;D Haggis
Post by Cotten on Aug 4, 2004, 4:19am
And don't forget that a Linkert gives your right knee some room!
(Practicality, in my book. Especially in cold weather.)
A lot of Evil Manifold Leaks result from hitting extended aircleaners with the knee when kicking. Especially when fueled by alcohol. (The knee, not the carb.)
In a world obsessed with what their machine looks like, I am amazed that the the clean, tucked-in appearance of a stock assembly has been out of 'fashion' for so long.
Post by 57pan on Aug 4, 2004, 10:57pm
OK, you guys just about have me convinced to put a Linkert on it. I'll keep my eyes open for one.
In the meantime, though, I need to get the Keihin tuned. I took a 70 jet and opened it up to 80 - it was still too lean. I opened it up to 85 - no more coughing and sneezing thru the carb, so I think that must be about right. Haven't had a chance yet to put fresh plugs in it and run it for a while at 1/4 to 1/2 throttle to see what the plugs look like.
Just a word about the method used to open up the jets (before someone tells me that it can't be done accurately enough). I used a set of tapered broaches (reamers) that are part of my clock/watch repair tools. Using these reamers I can accurately open up the hole in the jet by any increment that I want - I don't doubt that I could hold a .0005 tolerance, and they leave a very smooth bore.
Post by sleeper on Aug 5, 2004, 1:00am
57Pan, sounds like you're close/ if not right there, on the slow-jet.
It's helpful that you can drill your own jets bigger.
It's a common practice when tuning & Cheaper, than buying loads of jets..
I drill mine as well, as needed. ;D Then when I'm where I need it to be, I scribe the 'New' size on it.
My uncle used to repair watches, I remember his tools.
I use micro-drill bits..
At least you're not Way Over-rich on the slow speed now. That's a good thing till you find your Linkert.
I'm Big on CV's & making them a 2 bolt pattern bolt-on.
Post by 57pan on Aug 5, 2004, 4:33am
I think I've got it. I blasted the plugs and got them nice and clean, then went for a 10 mile ride. Coming down the road to my house I pulled in the clutch, cut the throttle, killed the engine and coasted into the driveway. I pulled the plugs and here's what they looked like:
I think they look pretty good. It's hard to get the color to come out right on the screen, but the ceramic in the center is off-white. Maybe they should be a little more on the tan side? What do you think?
Post by sleeper on Aug 5, 2004, 7:44am
57Pan, I think your pics are BIG enough !! ;D
Seriously, your Rear plug is running Richer than the front. For only 10 miles & blasted clean-somewhat plugs. They show quite a bit of difference.
Look at them closely, You got a New top-end there.
Did you pressure test your intake after re-assembly ??
Post by Cotten on Aug 5, 2004, 6:20pm
I see a slight difference, but not an alarming one.
I currently have one of my godchild Knucks in for service; Even with a drum-tight manifold, and the timing degree'd to where the images of front and rear timing marks (I use paint) are superimposed over each other with a strobe,....the plugs still burn with a minor difference.
