1981 XL500S won`t rev out...help?

[UFS207]

I was given a 1981 Honda XL500S that was in pieces recently. The bike was pretty much all there and the motor hadn`t been touched other than removal from the frame. I gave it to a bikeless friend and we got it running and semi-ridable within the space of an evening. The bike actually idles super smooth, doesn`t smoke and has very respectable low end power.

HOWEVER, the bike will not rev out at ALL. Anything over say an 1/8-1/4 throttle and the bike just gurgles and misses like crazy. It`ll rev out fairly well without a load on the engine though. I`m not exactly a newbie to dirtbikes so I really think the main is too rich. The thing that I don`t understand is the main is stock sized; 155 according to the clymer book. Is it possible to wear a main jet out this baddly??? Plus I always thought most street legal dirtbikes where jetted somewhat on the lean side to begin with for emission-related reasons. I should also note that the needle looked fine and as an experiment I cut a small groove above the single stock groove so I could drop it 1.5-2mm and lean the main jet out.....seemed to help but the bike still gurgles/misses like crazy.

Can we use XR500R carb parts on this bike (particullarly the adjustable slide needle and different main jet sizes)? All the places I usually order from online only list the 1981 XR500R, don`t even mention the XL500 at all.

Any help is greatly appreciated. Also, could anyone direct me a good online source of info for these bikes? Google doesn`t turn up much and the one site I found dedicated to these old XL`s is a german site.

 

[plane_ben]

Is the air fiter good and clean? Valves adjusted to specs? New spark plug? If the jetting is stock it should run better after checking these three items. Oh on other thing. Check the float level in the carb. Could be low. If to low it would idle fine, but stagger under load. Hope this helps

 

[UFS207]

Hey man, I want to thank you for responding.

We pretty much fixed the problem or at the least affirmed my suspicion that the main jet was way too rich. We`d already done the basics: clean filter, new plug, valve lash adjustment, cleaned the carb with compressed air/carb cleaner and set the float height.

Amazingly enough the main jet on this bike interchanges with just about any Keihin motorcycle carb made around this time (70`s and 80`s)...maybe even later model Keihin carbs. I took a #115 main out of a spare set of carbs I bought for my old CB750 and tried it just for the hell of it and it threaded right in. Bike is definately too lean now (pops on decelaration) but revs out nicely and pulls like a raped ape. We ordered a bunch of main jets to try in the bike from #125 - #150 so we will get it dialed in correctly for sure.

I just thought I relay the info incase somebody else winds up with a poor running old XL and searches these forums looking for help.