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HONDA 250r ATC 1982 - how do i identify the carb to buy a jet kit,

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HONDA 250r ATC 1982 - how do i identify the carb to buy a jet kit,

New User | Posts: 1 | Joined: 05/09
Posted: 05/17/09
11:06 AM

Confused are all mikuni 38mm carbs the same? i bought a 82 honda 250r that someone just put an (used) aftermarket carb and reed cage on it, and blew it up the first 2 minuites i rode it. overheated and now there's almost no compression. im kinda new to messing with carbs & tuning 2 strokes. it's a gold mikuni 38mm(i think, i measured it with a measuring tape - not too precise) with a canister that has a hose running to the 3piece intake manifold. im assuming it was way too lean. what size jet should i start with when i get a new piston in it? i need a jet kit, but i dont know how to go about getting one for the carb, ive been finding them for the 82 250r, but the aftermarket carb will be differant, right? the trike has a stock bore as far as i know, but im not sure. i also have a dg pipe and silencer thats loud as he!!. i havent taken the top end off yet, so i dont know if i will need to bore it or not. ps, i mixed a high quality 2stroke oil with 89octane gas and octane booster 20:1. what size bore is stock. any help, or suggestions would be great, thanks.  

TrikeLvr TrikeLvr
New User | Posts: 2 | Joined: 11/09
Posted: 11/11/09
09:55 AM

Hi,how are ya? I have an 82'R with a 34mm carb. wich is from an 85'R and it hauls ass. Imo = that carb is too big. My brother kept on blowing up his motor by not adjusting the timing w/ timing light(magneto). His actually spit the copper head gasket out lol. Carbs are real tricky. That carb is probably off of a newer 250R or TRX250R(water cooled). Does it have a reed spacer? You have to order jets for the Mikuni 38mm for a 250. You can buy a pack of all different size jets and try them all starting with the lowest and check plug throughout tests.
Yeah, my R is pretty loud also w/ basani pipe. Gotta love 250R's. IMO...Check the timing thing=the adjustment is made while the stator cover is off and engine running.  

TrikeLvr TrikeLvr
New User | Posts: 2 | Joined: 11/09
Posted: 11/11/09
10:10 AM

The ATC 250R is a high-performance ATV produced by Honda from 1981-1986. Early models (1981-1984) used an air-cooled, 248cc single cylinder 2-stroke engine. Fuel was fed through a 27 mm ('81-'82) or 30 mm ('83-'84) round-slide carburetor and reed-valve intake. Power was accessed through a close-ratio 5-speed transmission with a manual clutch. Later models ('85-'86) used a liquid-cooled, 246cc single cylinder 2-stroke engine with a 34 mm round ('85) or flat ('86) slide carburetor and reed-valve intake. The 85-86 models were upgraded with a close-ratio six speed transmission with a manual clutch.

A little bit on jetting.
1. Look to see what jets are in your new carb. Main and pilot.
2. Go to your local bile shop and buy at least 2 up and 2 down, main and pilot. If you can go 4 up and 4 down. I think I have every Keihn main jet availible and use them throught the season.
3.Get 3 or 4 B8ES spark plugs.
4.Drain tank and fill with fresh fuel (mix another topic)
5.Run it hard till hot.
6.Do a plug chop. Important to do this right!
7.Pull the plug and check color - First time out use the plug thats in it now.
8.If your plug is chalky white go fatter with your main jet. If its wet and black go skinnier.You want to see a cardboarrd
brown color on your plug.
9.Do not try to go out with a group of people when you are trying to figure out jetting. They will only tell you that you should have gotten a 4-stroke!
Humidity and temp will really affect jetting.