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1980 XL185 - Need input

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We acquired a well used 1980 XL185 that didn't run.  Tried to clean the original carb, but it was so pitted and the bowl sealing surface was cracked that I replaced the carb with a new one from eBay (same diameter as original, I believe it is 27mm), removed the rats nest of wiring that was cut and stuffed into various locations and installed just the necessary wiring for the ignition and a kill switch.  Removed the rotted out stock muffler and made a pipe that goes into a DG Universal muffler, checked the valve timing, lift, cam chain tension, replaced the fork seals, new brakes, chain guide from a KTM 80, new front and rear knobbies, knuckle guards, CR250 foot pegs, straight pull throttle, new levers and a new seat cover. I put an insert into the muffler to give it some back pressure to mimic the old muffler. It sounds nice and has been a good little runner.  Doesn't burn any oil and has good compression.

 

It has been running very well with the stock foam air cleaner/box assembly.  I am putting on side plates from a XR on it and in preparation I built a new airbox for the new K&N cone air filter, as the stock box will not work with the new side plates.  I figured that the new filter would have less restriction and that it probably would need new jetting. What I have is an engine will start and idle perfectly, but the rpm will not increase.  It initially starts to accelerate but then bogs down and returns to idle. The carb that I originally bought for it from eBay does not have provisions for changing the jetting.  Listening to it, it sounds like it is not getting enough fuel. Since it was just running perfectly up to replacing the stock foam filter with the new free flowing K&N, I tend to think that it is a fuel/air ratio issue.  I also took the insert out at one point to see what it sounded like.  It sounds really throaty and would like to run it that way, but I think that will also change the airflow through the engine as well.

 

Would like some input as to what steps to take or a recommendations,  what carb to install, jetting, etc.  Also, if I should recheck the valves. 

 

How large of a carb can I put on this?

 

Thanks!!

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Quick update.  Set up: Muffler restrictor out and free flow K&N:  When the choke is set about 1/3 closed, it runs perfect.

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I figured closing the choke butterfly would simulate the restriction that the foam filter gave.  Now with the free flowing filter and easier breathing without the muffler restriction I need to find a setup that will take advantage of this.   Suggestions???  

 

Back in the 70-80's when I did the setup on my 2-stroke RM's we went up 6mm in diameter on the Mikuni carb when we changed the reed valve and modified the expansion chamber.  Don't know much about 4-strokes, but I would imagine that they are fairly similar.  Maybe using the carb size/jetting setup that is used on a XR200 would work.  Hoping someone here has already driven down this road.  Would save a lot of dead ends turn-arounds.  Thanks.

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So this ebay carb cant swap out its jets or somthing? Because thats whats needed and if you cant then i would look for an OEM carb and rejet it. :/

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Looking now at two carbs, as I can find them on the web.  The first is the Keihin 016.144 PKW 28mm carb. The other is a Mikuni TM28 Flatside (VM28-418)

Any reviews?

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Looking now at two carbs, as I can find them on the web. The first is the Keihin 016.144 PKW 28mm carb. The other is a Mikuni TM28 Flatside (VM28-418)

Any reviews?

never had either of them but i would go for the keihin because the pwk is a common carb and parts are abundent

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