Carb Jetting 101: Terms, Tips and Jetting Theory

**Dirtcrasher** · 01-23-2009, 12:43 PM

Suddco has a book for tuning the VM and TM carbs. It took awhile, but I did find something similar for free here:

http://www.mikuni.com/pdf/vmmanual.pdf

Hopefully it will help me out a bit, headed back out in about an hour or so

**daniel_250r** · 02-09-2009, 04:35 PM

i have a carb question my 200s will never idle right i adjust the idle screw it idles at a nice pace, give it some gas and it takes a really long time to go back down, week later i start it up and its idleing really fast and i didnt use the choke or anthing

**Dammit!** · 02-09-2009, 07:02 PM

Have you tried adjusting the air screw? I'd richen it up a bit and see how it goes. Not sure which direction is richer on those carbs though.

**Mosh** · 02-09-2009, 07:09 PM

My 70 and 90 carbs are stock and were doing this..

Over time, the idle speed screw causes the slide to get rough.Then the slide will not always return to idle, or snap past the burr in the slide, and idle too low.

Remove the slide, and you will see a ramp section where the idle screw contacts the slide.You will see a divet, or rough spot in the slide ramp,from the screw contacting it for so many years.
Take a fine tooth file,and file that smooth again..Then re-assemble and adjust..
Just a simple tip before you go changing jets..

**daniel_250r** · 02-09-2009, 10:38 PM

alright thanks, a part of me also thinks a clamp is loose or hole is in a boot causing an air leak but we will see

**ThinktwiceZ71** · 02-12-2009, 09:23 AM

hey guys , i just rebuilt my 200s engine , while doing it i rebuilt my carb also with a moose carb kit from dennis kirk , it had a new needle , seat , pilot jet , air srew , main jet (plus the usual washers gaskets and orings). All were the size that was in it before the rebuild. here is the thing that confuses me , before the rebuilt it was running rich , black carbon soot on the plug when checking it , but i had peace of mind knowing i would never be lean. now after rebuild and setting the carb back to factory specs i take it for a little ride last night and it rides awesome , but the plug is damn near white. I called the honda dealership and they said to lower the clip to position 4 (3rd is stock) ....i did that and i turned the air screw in a little (add a little more fuel) and the plug is a light grey now. do i need to go to a 105 main jet ? (100 is stock) along with a 35 pilot jet is what is in it.

i have a cob jobbed air box lid on it that does not seal , and i have a aftermaket pipe that leaks some too......i know i should get it fixed but i am going to run it like this for now.

i just don't get how i was really rich with this setup before , and now after rebuilding with the same size jets and stuff , i am way lean.

anyone ?

**benjoefoe** · 03-02-2009, 08:57 PM

I bought a brand new factory replacement carb for my 1985 Honda 185S, the first day I put it on it ran good, 2nd day it was sputtering a little so I tryed adjusting the idle and pilo screw but only screwd up the settings, now I can't get it to start. Is there any standard setting these screws are set at in the factory? Anyone maybe have pics or advice I can go by?
Thanks!

**ledgettc** · 06-25-2009, 04:53 PM

Thanks for the great info...
I have an 86 200E yamaha that had been dying intermittently. I can run for 4-5 days w/o any problems, then boom be out on a run and it will just die. Once I get it started it will idle but once I go to take off it dies at less than a 1/4 throttle.

I thought I would pull the float bowl and make sure that the fuel is not contaminated, but that is about the depth of my knowledge on carbs.
Do you have any thoughts?

Thanks,
Chris

**mohadib** · 08-03-2009, 05:00 PM

Can you do plug chops in netural setting still? Sorry if this is a goofy question. Thanks.

**NOS_350X** · 08-03-2009, 06:29 PM

No, must have a load on the enigne.

**jaredj** · 10-02-2009, 02:04 PM

i have 110 1980 atc that i just picked up. I changed the plug, air filter and installed a carb rebuild kit. The bike cranks on first pull and idles fine. If i ease into the throttle and then open it full it works fine, but if I go straight into wide open throttle it bogs out. Not sure if bog is the right word, but basically it wont do anything. When riding as i shift it does the same thing. any ideas? my only experience is with lectron carbs. any help.

Thanks,

**scottp597** · 10-18-2009, 09:25 PM

The guide says bogging is a lean condition, but when adjusting the pilot circuit if it bogs off idle its rich??? I am confused by this

My machine bogs off idle, I believe it is too rich but I'm not sure what to adjust. Turning the screw out to like 5 turns clears it up I believe. So it must be rich, I'm thinking about raising the clip or getting a smaller pilot. Not sure

**austinkay2k7** · 11-03-2009, 12:53 AM

Ok, very informational and helpful article, but i need more info. my 83 atc 185 will run well with the choke on, and will idle great with the choke off, but will not run at all above idle with the choke off. i dont know what to do.... thinking about buying a new carb....

**MagicJames** · 11-03-2009, 10:53 AM

Originally Posted by austinkay2k7

Ok, very informational and helpful article, but i need more info. my 83 atc 185 will run well with the choke on, and will idle great with the choke off, but will not run at all above idle with the choke off. i dont know what to do.... thinking about buying a new carb....

Is your carb clean? That would be the first step. Take your carb apart and take all the jets out and clean out your jets, or replace them.
Get a can of carb cleaner and clean out every little nook and cranny.
Re assemble the carb and if you're still having problems i would check your idle. jet, it might be too rich.

**Just-Tri-It** · 03-30-2010, 02:35 PM

I have a stock 85 Z except for K&N air filter and DG silencer. She idles well but when you gun it or stab it to rev it up and let it rev back down while sitting still it doesn't have a clean crisp rev. If has the rapid misfire but not the bog. About like the rapid misfire you get when you 're doing a WOT in 4th or 5th gear. Just a fast misfire type sound. Like it really wants to get up and run but something is holding it back.
But it's when it's sitting still that I'm talking about for now. This is what I have done to no avail.
The manual calls for a 470 stock main jet which is what's in it. I have the chip on the 3rd slot. Air screw 2 turns out. I have changed the main jet from a 400 to a 500 in increments of ten and worked the air screw from one turn out to 8 turns out and it's the same on all the jets with no help in rev. for a clean rev.
I'm wondering if I'm dealing with the wrong jet for getting a clean rev when she's just sitting still. Maybe different jet is responsible for that area when she's just sitting and idling. I know it may be electrical.
I thought about changing the reeds to see if this would help. Thanks for any suggestions.

Also I can't find this thread front the new board menus. I had to use a saved link to get to it. Is it still listed under the Trikesylvania Forums or am I just over looking it?
Thanks

Thread: Carb Jetting 101: Terms, Tips and Jetting Theory

Thread Tools

intermittent stopage during throttle

Help ME, need more info

1985 Triz Jetting Question