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Discussion Starter · #1 ·
I am having carb problems with the ole' Tilloston HD87A carb on my '72 Arctic Cat Cheetah 440.
I rebuilt the carb prior to the snow flying and I had the sled running good for about 40 miles then she is bogging out at top end, idlng rough and fouling plugs. I did not remove the welch plugs and that is most likely the problem. I started at 1 1/4 turns for high and 3/4 for low and ended up at 1/4 turn for the high and 1/8 turn for low for carb setting.

I have been told to throw that HD away and put in a mikuni carb but do not know which one would be best. Any advice on what type/size of mikuni carb to use is greatly appricated.

Jeff
 

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Discussion Starter · #2 ·
follow up: I flooded out the engine and put a 1/4 tank of gas in the crankcase and muffler. WOW!!!!! I remove the plugs, carb and exhaust. Went to the shelf and got the dewalt cordless drill using the appropriate socket and extenstions I connected the socket to the clutch bolt and began turning over the engine and had a fountian of gas spewing from all open engine wholes & vacuum line. I knew then I had issues!!!! I assembled everything, got the engine to fire up but could not adjust the low or high idles. I closed the high speed and tweaked the low and got it to stay running (about 1/2 turn open). If I opened the high speed (just a crack) the engine would race. I removed the carb and began to disassemble and research on line what the problem is. From what I figured out.....a clogged or bad ball check valve. To get to this you have to remvoe the welch plug. Needless to say I ended up damaging the brass under the welch plug, by use of the portable drill. Suggest using a drill press and setting the depth so you only drill the welch plug, as this brass fitting is just under the aluminum plug. OFW!!!! Use a small punch to pry up the welch plugs. I used a thin punch and pushed the ball and retainer out. It came out thru the venturi (center of carb) not sure how it goes back together, then I tried to remove the brass (the one I drilled on) as it was ruined anyways. It is press fit so I had to remove the choke assembly and push on the brass showing in the venturi and got the needle nose and pried the sucker out from the hole the welch plug covers up. Yea it is trashed now.. I hope the rebuild kit I ordered comes with another or I will be looking for a another HD87A. I took pics of everything sand put them in a word doc...so if you need them give me a shout. [email protected] subj line: Tillotson HD pics needed.

ANYONE HAVE A Tillotson HD87A for sale just in case??????????????
 

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Installing a Mikuni really isn't that hard. Just have to find a flange that fits, a nice VM34 (I've seen VM34s, VM36s, and VM38s used on old kawi 440s) as well as a mikuni fuel pump. Now for the tricky part, a vacuum supply hose for the pump has to be drilled. I'm by no means an expert but I know that plab on arcticchat put mikunis on his '72 Panthers. Heres one thread with some good info

hope this helps!!!
 

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Sounds like your needle valve is stuck open.

One thing I have learned with the Tillys/walbro, is Dont strip them down to far. Unless the carb is in bad cond.

Dont use a cheap after market kit, get your hands a factory kit.

To me! If the carb is in good cond. I just put in new diaphrams, gaskest, I reuse the original stuff, always seems better, most dont have enough use to be bad, if they are put new in.

here is a good link:

If you switch carbs. you will also have to put new gas, choke cables.
 
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