1984 honda xr500r starting question.

[bucksaw86]

so I have this problem. I just put the carbs back on my bike after taking them apart to clean them. I tried starting the bike for the first time and I kicked it over tons of times with the choke on and could'nt get it to fire. Finally I got it going and once it warmed up It would barelly run with the choke off. any ideas why this would be happening? the bike is near mint and has great compression and spark. and if I go past half throttle it starts sputtering and backfiring. I need help:banghead:

[Horri]

So what have you done in relation to this thread

https://www.thumpertalk.com/forum/showthread.php?t=888363

I'd advise making sure you have the airscrew set right and renewing the defective washers and getting a new AIr cutoff valve and gaskets,,.ie semi reco the things or buy some known good used XL/XR600 carbs and change the jets round to suit. Check the floats aren't cracked and full of gas as well and clean the carbs again with compressed air etc etc..Some internal bits in them do wear out and can be replaced..small brass parts which I have no idea of the name of now. When I put some of those new internal parts in my XR600 carbs the thing was farting/burping and carrying on for a while until the gas got to all the right places..Worrying at the time but they eventually sorted themselves out and came right. Never ending carb problems sometimes...Perseverance is the key..

Edited March 23, 2010 by Horri

[bucksaw86]

i sealed the metal fuel tube that connects the carbs with loctite gas and oil adhesive to stop the fuel leak. cleaned all the jets. im not sure what the air screw is suppose to be at. its 1 1/2 turns out right now and I do not have any manuals on the bike. I can keep the bike running with the choke off but if I go past 1/3 on the throttle its starts burping and bogging and a little bit of back firing pretty much gutless if I tried to ride it with the choke off. I was told the bike sat for a few years and didn't get used.

[Horri]

I assume you have renewed the fuel..I've got to go for a bit but someone else may be able to help. I'll dig up a manual and check the airscrew thing but what you have sounds about right..that of course doesn'r mean it's perfect for your bike..

[bucksaw86]

yes I put brand new fuel in the tank. I didn't tear the upper parts of the carbs down though like the air cut-off valve I didn't touch anything around there. I probly should just tear the carbs fully apart. Its gotta be something simple I would think.

[roostmaster1]

cloggged main jets...

[Horri]

Hmmm..I wouldn't advise you tearing the carbs entirely apart unless you have a manual. Even then they are not something thats a basic wham bam thankyou mam operation.. They are quite a complicated piece of machinery when you get them separated and start pulling out slides etc..The best thing in my opinion for you to do would be get another good secondhand set. In saying that replacing or checking the Aircut off valve should be doable..Examine it for pin holes..it's a metal and rubber type setup and is I think from memory on the outside right of the lefthand carb,,It's held on by three phillips head screws. Go to far inside and be prepared for complexity..Course while your there give the jets a thorough going through with fine wire or use compressed air to make sure their are no blockages. I'd also say you should do a proper job on those rubber grommets on that connecting pipe. You should be able to get replacements for those from a good bearing/seal shop. Proper bearing places sell all sorts of sizes of rubber seals even down to that tiny size,,they won't be Honda but they should be adequate.

Edited March 23, 2010 by Horri

[valvesrule]

Any time you rebuild a bike carb you need to blow all passages clear with high pressure air. If water, dirt or carb cleaner is left anywhere in the carb it can stop the flow of fuel and make the bike a hard starter in the least. Surface tension of water can stop the flow of gas entirely thru tiny jets, orifices and passages. Many times if you can get the bike to start vacuum will pull the offending matter thru but not always. It's not like a car or other vehicle with a fuel pump/pressurized system. Head pressure from the tank and vacuum from the intake are pretty low to pull/push foreign matter out.

[bucksaw86]

thanks for the help guys. I definitely have a good starting point now. by the way if the air cut off valve is bad, what symptoms would the bike have while running warmed up with the engine choke off?

[valvesrule]

If stuck open or leaking diaphragm it could do what you're experiencing. Usually some manifestation of running lean. I'm wasting time on TT right now instead of fixing one of them on an XL600. Make sure the little o ring isn't missing or doesn't get left out. Any pinholes in the diaphragm can be a problem. The seat of the valve itself needs to be clean and free as well. The air cutoff is in the middle, on the inside of the left/primary carb and will require almost complete teardown to inspect. The 2 carbs do have to be separated to get to the 2 phillips screws holding the cover on. If the slides move freely don't bother removing them just take the top covers off and carb cleaner the bodies with slides in. Only reason to pull the slides is to lean or richen the needle settings. XLRAT likes to change slide cutaways and needles but for the inexperienced the less you mess with the better. Make sure there is an o ring on the air screw. Some bikes seem to run fine with them missing others not so much. One strand of wire from a wire brush usually works to clear all air and fuel passages. Blow all passages out with compressed air. Head pressure from the tank is too low to clear them out. when you reassemble make sure the slides hit WOT at the same time. as this being wrong can cause other caburetion problems. Again XLRAT sets them differently but he is very familiar with what these carbs need.

Edited March 24, 2010 by valvesrule

[bucksaw86]

alrighty thanks alot, I now have a good idea what to do to get my bike running right. If all else fails after this, I'll have to start looking for some good used carbs. summers on the way, gotta get it fixed soon haha.

[DGXR]

If the motor starts sputtering at around 1/3 throttle, that is about when the 2nd carb kicks in, may have something to do with the problem. The secondary may be kicking in too soon, or too late