1980 xj650 enrichment circuit

Hey everyone! I purchased my 1980 xj650 maxim a couple of months ago for a shop project for me and my boys. The guy I bought it from sent me a video of the bike idling and being revved up. He told me that while videoing he noticed fuel dripping and the bike shut off. I assumed it was just a stuck float so I took the carbs off and went back with new main jets, pilot jets, float seat and needle also. I also removed the air mixture screw and replaced the oring and washer. The air mixture screws were backed way out. Not 1 3/4 - 2 1/2. I reset to 2 1/2 turns out. When I leave the bike alone for several hours and come back to try and start again the first few turnovers it sounds like it is going to fire up but then dies back down. I read in one of the forums about the starter jet and enrichment circuit well, so I took the float bowls off again and tried to do some cleaning there. I'm not getting a stream through when I hit that circuit well with carb cleaner. Is there any tips anyone can offer on getting those cleaned good. Also does it sound like this could be my main problem? Any help would be greatly appreciated!

 

Also I'm not 100% sure the stock fuel tank is on the xj. Looking at images of 1980 xj650 the fuel tank looks rounded and smooth. My fuel tank looks more like a seca model.According to what I have read there is supposed to be a vacuum hose from my number two carb to the petcock but my fuel tank petcock only has one nipple for fuel flow and no prime, only "on off and reserve." Coming off my number two carb is a short hose for venting with what looks like a white plug with a small hole in the center. Do I need to get a new pet cock with a vent line or is this an ok modification?

 

As long as the nipple on the intake boots are all sealed(capped) and not leaking you will be fine. Just remember to turn the petcock to off when you park it should your float needles leak you may end up with a crankcase full of fuel and an empty fuel tank. I have a manual petcock on mine like you describe

 

Thanks I put my finger over the vent line and felt no push or pull so it's capped with a plug. I cleaned the starter jets and enrichment circuit well the best I could with a nylon bristle, carb cleaner and compressed air. Got the carbs back on, engaged the the choke and she fired up but wasn't strong for long before it died back down. I cut back to 1 3/4 turns on the air mixture screws (not sure which direction to go). I'm not sure if I need to adjust my idle knob either. With the choke on the Rpms were at about 700-800 (again not sure which direction to try. The motor was warm but still didn't want to stay running.

 

The enrichment circuit serves the same purpose as a choke and should not be needed except when the engine is cold and you are starting it. Once warm the engine idles solely on the pilot circuit. If you are having idle issues I would revisit the. pilot circuit. If you are having a problem getting the passages clean you can boil the carbs for 10-15 minutes and the should remove any varnish, etc.

 

Warming up on choke the bike should run at around 2000+ rpm, choke off 1000 minimum to 1500 when warm(below 1000 the oil pressure can be a bit low, especially on an older motor)
Note: if the idle is set too high, the bike will try to exhibit similar symptoms as it being too low.
I recommend backing out the idle screw untill it doesn't touch the stop, set at stop, then advance one turn, start the bike and use throttle to keep it running then slowly advance untill desired idle speed is reached.
Hope this helps

 

Per the petcock, chit wood is correct.
The OEM petcock used engine vaccuum to open the petcock when the bike is running and close it when off. The prime feature bypasses this to fill your carbs if they are empty from being drained or serviced so you don't have to crank the motor for 5 minutes to fill them up.
The OEM petcock is more convenient and as a safety feature shuts off fuel if you dump the bike and it stalls.
If running a manual just be sure to open and close it as needed.

 

Thanks a ton for the information so far! I believe I'm going to have to take tabaka up on his word and pull the carbs again. I ordered a rebuild kit when I bought the bike and replaced th main jet 110, pilot jet 40, jet needle, float needle and seat, main air jet 195 (if I remember right), pilot air jet 50 (again not sure of size), float bowl gaskets, and the air mixture screw.That was all the rebuild came with and to be honest I wasn't just aching to take the carbs apart from the rack. I was kind of hoping I wouldn't have to because just days before the purchase I had seen it running. I'm new to the motorcycle mechanic work so I'm learning as I go. I just wish I had found this place before I even got started on the bike! But being that I already have those parts of the rebuild can anyone give me direction on what's left that I will need to purchase? What size o rings for the fuel rail and what else will be left to replace? Also I don't really want to spend the money for an ultrasonic carb cleaner for just using once, any other methods I can do as extra cleaning to add to boiling? Before I do the boiling i have to ask what to boil them in? Water or chemical? Do I only need to remove rubber washers, o rings, and diaphragms before boiling? Again thanks for all the help!

 

When I boiled mine they were stripped down but still on the rack so the o-rings were not removed. If you are going to replace the o-rings I would do that before boiling them. I boiled mine in plain water, but I have read where some have used some type cleaner, and some have even used lemon juice! I have an ultrasonic cleaner and for varnish in the carb I think boiling is much better because of the much higher temperature.

Also, unless you got your rebuild kits from Chacal, the float needles may be a little longer than the original ones so you will have to be sure you wet set the float heights. I assume you are using all stock size jets.

 

Ok great I will definitely give that a try first! How long did you boil them? You are also correct I went back with stock jets. Although they had already made some modifications, I believe they were headed in a cafe racer direction because of handle bar style and they had removed the seat and back fender. The air box was also cut and modified with sheet metal for more room I'm guessing. I Have the stock air filter so when I attempt to crank the bike I have just been wedging the filter in place and leaving the butchered air box out of the picture. I'd like to get pods for the bike but want to get it running strong with everything stock first, well minus an air box. From info here that is my best bet before even getting pods.

 

Also is muratic acid the best way to clean the rust from the fuel tank? The tank needs a good cleaning out!

 

Im not an expert but I've never boiled carburetors... In 16 years... Good cleaners and a lot of time, tiny jet cleaners and patience work best for me, if you have new parts, re clean, re set floats, retry.
As Per muriatic in the tank, yes it works well, however rinse with baking soda and water to neutralize the acid.
Then I recommend 10:1 mix gas, few hundred ml, and slosh around a few times to "seal" the rust.
Add a blob of 2-stroke oil to your gas once and a while, it will stop the rust from coming back, working for me

 

Personally Berrymans 1 gallon carb dip is my favorite it has a basket in the container and can be bought at Autozone and has enough to do several carbs . After all the rubber seals are removed soak for about 1 hr per carb . I noticed some things in your post , you stated you replaced needle and seat...did you check and adjust float height? 17mm float height measured from the flame to end of the float gets you close , wet set better ,with carb assembled and bowl full with a piece of clear hose on drain nipple hold tube up to top flame, open drain screw see if you are within 3mm of flames. If it above this you will need to adjust tang on the float . Same if it is lower .

 

Sorry I should have mentioned that I set the float levels within spec (3mm-1mm) but it's strange because I'll mount the carbs and have to bump them a little because it seems like the needle gets stuck and let's a carb flood. With the bowls off I've made sure that the floats move freely without getting stuck. And the needles slide in the seat good. That's what had me concerned about the gas tank and petcock being different I thought maybe it was affecting float bowl levels somehow or is it normal to have to give them a little bump after getting them back on?

 

Not normal. Off the bike the carbs are level for wet setting. On the bike the carbs are not level. Sounds to me that one or more needles are binding when on the bike. Did you get the needles and seats as a set? If not that might be the problem . I got mine from Chacal as a set and elected to use brass needles rather than soft tipped needles and I have had no problems.

 

^^^^+1 on the brass needles that was what I went to.

 

The viton-tipped needles work great too, so long as you get the correct set from the correct manufacturer.


Back to the fuel levels.
You wrote that you set them to 3mm-1mm, which I read as being that you either set them to be 4mm below the bowl lip, or being somewhere betweeen 1mm and 3mm below the lip.
Can you clarify that you meant the fuel levels were set to 3mm, with none of them being more than 4mm below, and none being less than 2mm below?

 

I have the levels between 2mm and 3mm from the lip of the carb body. I butted my ruler to that lip with the carbs level and measured down 3mm I was shooting for a perfect 3mm but thought between 2-3mm was ok. The needles and seat came with the rebuild set for all 4 carbs. I'll admit that they came with a needle that looked completely different it didn't even have the little spring clip to stay attached to the float tang, so I read a review after discovering this that the float needles weren't right for the bike. The old needles I removed had a rubber tip, the new needles had just a metal tip. So at first I didn't even try those needles I ordered more needles that had the rubber tips and looked right. Unfortunately that was a waste because those needles that looked right wouldn't seat properly so every carb poured gas from the air jets. I took the carbs off and put the metal tip needles in and they seated just right when I was setting the levels but when I got them on the bike and started adding gas one carb started pouring gas. I bumped them and it stopped flooding. I sure wish I had known about chacal so I wouldn't have done all this guessing! I hate to buy more needles and seats but is that my best bet? Or is the float needle issue I have gonna be fine since I can bump it to seat it. Also since I wasn't sure about the petcock and the tank gas some bad rust I have been feeding the carbs by putting a meat syringe in the fuel line (it fits perfect) and adding gas through that. I leave the syringe open and just make sure it's full when cranking. It seems to be pulling the gas in so I guess that's an ok substitute?

 

I'm not positive but I think the rebuild kit came from USA warehouse.

 

I sure would’t feel comfortable knowing I had to bump the carbs each time I shut the bike down. With 4 carbs I certainly would not feel good about the middle two carbs for sure. I think you should contact Chacal and get the correct seats and needles. I would also try to find the correct petcock even if you buy a used one on eBay and rebuild it. Gas in the oil is dangerous in my opinion.