New guy

[treycotiii]

Just bought a 1987 Foreman and have carb problems. I think the main screw is not set properly. Which way is for lean and which way is for rich?

[jen]

Typiclly screwing in leans it out and CCW makes it richer.  But I would at least run/ soak fuel system in Sea Foam before adjusting.  How is air cleaner etc>?

[M48TANKER]

On 1/6/2026 at 5:50 AM, jen said:

Typiclly screwing in leans it out and CCW makes it richer.  But I would at least run/ soak fuel system in Sea Foam before adjusting.  How is air cleaner etc>?

Yes, what Jen said. I'm working on a 1998 Artic Cat 454 for my brother right now. (stumble at high rpm in 4th and 5th?)

I believe most "mixture screws.....located on the bottom rear of the carb.....can be set at two turns out as a starting place. Adjust in (leaner) or out ( richer) to achieve the best idle. Turn the screw all the way in and then back it out counting the turns CCW. Somewhere around 1&1/2  to 3 turns should work. Most of mine set at 2&1/2

 

Please correct me if I'm wrong!

[jen]

Welcome and thank you for your service!  I am in awe of the men who sit in the steel behemoth (Job 40-15) M48 Patton .  It was a blessing to the military during the Viet Nam War.

[geezer99]

You got me with mentioning army tanks!  I have fond memories of climbing all over the walker bulldog tank parked at the National Guard armory when I was a kid.  Even better when they drove it in parades.  If it was hot, the tracks would leave conspicuous marks on turns.  

To put myself through college, I drove HD21 and D8 crawlers pushing scrapers and clearing land.  Good times, and I met some interesting charactors.

thanks for prodding good memories,  tom

[M48TANKER]

Geezer99,

There is just something about operating heavy equipment that makes you feel powerful! After I got out of the Army, in 1970, I returned to the construction business. My father, E.J. Roper, had been a Custom Home Builder most of his life and I followed in his footprints. I spent the next 42 years building homes and office buildings. 

When you are the General Contractor on a jobsite, you can often get a heavy equipment operator to let you operate his equipment just for the fun of it. They enjoyed some time in the shade and I got to operate backhoes, dozers, skid stears, end loaders, track hoes, "Lull" forklifts, and I once operated an old U.S. Army crane, and that thing was a handful.

Great fun😁

[Savage3]

https://www.aservicemanualpdf.com/Samplepages/SM-1986-1989 Honda TRX350 TRX350D Repair Manual.pdf?utm_source=copilot.com

[Savage3]

You need to determine which carb was installed, i believe the early models had a variant with a second bypass screw. The pilot screw is generally set at 2 1/4 turns from the factory. Good starting point Bud.

 

Generally speaking, if the screw is on engine side of carb, it usually adjusts fuel. If on air cleaner side of carb, it adjusts air.

Many times, ( you can tell by reading plugs) if it is lean or rich. Most common problems i see are lean, the idle circuit gets varnish from ethanol and sitting.

Edited March 8 by Savage3
More informative

[Admin]

@Savage3 thanks for posting the manual. I added it to our library and it is now available here: 

 

 

[Savage3]

On 1/4/2026 at 1:43 PM, treycotiii said:

Just bought a 1987 Foreman and have carb problems. I think the main screw is not set properly. Which way is for lean and which way is for rich?

FUEL SYSTEM TROUBLESHOOTING

 

Engine cranks but won’t start  

• No fuel in tank  

• No fuel to carburetor  

• Too much fuel getting to cylinder  

• No spark at plug (ignition malfunction)  

• Air cleaner clogged  

 

Engine idles roughly, stalls, or runs poorly  

• Idle speed incorrect  

• Ignition malfunction  

• Rich mixture  

• Lean mixture  

• Air cleaner dirty  

• Insulator leaks  

 

Lean mixture  

• Carburetor fuel jet clogged  

• Fuel filler cap vent hole blocked  

• Fuel filter clogged  

• Fuel line kinked or restricted  

• Float valve faulty  

• Float level too low  

• Intake air leak  

 

Rich mixture  

• Starter valve stuck open or damaged  

• Float valve faulty  

• Float level too high  

• Carburetor air jet clogged  

• Air cleaner dirty  

[Savage3]

Check inline fuel filter as well, make sure you have good flow to carb by removing fuel line and letting it flow into safe container.