Need help with gas leak and one cylinder on Maxim 650 1981?

:?: I bought a 1981 Maxim 650 recently. It runs nicely and looks nicely except for the following:

There is a gas leak and the number two cylinder spark plug appears to be fouled up. (I have changed all four plugs, oil, oil filter, and air filter) I checked the pipe for the number two cylinder and sometime it gets hot like the others and sometime it is just warm.

Gas sometime leaks from the overflow tube of the air box.

When idling and there is plenty of gas, revving the engine makes more gas leak out (sprinkle) of the left exhaust muffler hole.

The bike sounds just fine and runs just fine. It is a pretty bike.

My question is: Is this a carb problem? Is this a cylinder problem (the spart plug for #2 cylinder turns black and has liquid on it sometime)? Why does it run and sound so good when one cylinder may not be firing or have a problem?

Any help would be appreciated.

 

Sounds like you might have a sticking float valve. You can try gently tapping with a screwdriver handle or something similar on the float bowl.
Might be time for a carb cleaning.

 

Thanks. I am new to biking so I do not know the terms too well.

I will try tapping on the bottom of carb #2. Is there anything else I can check/do?

Sam
81 XJ650H Maxim

 

Welcome to the world of XJ ownership Sam. I, being from Sac and owning an '81 650 H myself, can relate. Your first lesson, get a Haynes manual. Second, read through the book briefly to get familiar with the terms. Third, pull the carbs and clean them. From there I would check the compression and I would check the valve clearance. This is to get your baseline of what you have. I had an identical issue with my baby after my brother did an oil change on the beast and put 5 quarts of oil back in the case. Blew the seals out. I hope this is not the case for you. Depending upon what you find, you may have cracked rings on number 2, a stuck float, or valve guide issues. Overpressurization of the case can come from a few sources but lets find out how sound the motor is first. If you have problems understanding this, A&S Motorcycles is the first place I would send you. They are in the yellow pages. If you need, I'll see if a few of my buddies up in Sac would be willing to get together with you to show you the ropes (hope they answer the phone). Get started on your homework and post what you find. Good luck!

 

Here's a link that gives alot of info too.

http://www.dansmc.com/mc_repaircourse.htm

 

Thanks so much, guys. Robert, when I changed the oil, I had put in about 2 qts or so and checked the level.

I have already ordered the manual.

Is A&S motorcycles the same as A&S BMW motorcycles? I have seen that on I80. There is also a Yamaha dealership, PCP motors, here. Do you know anything about that?

What would they change usually for diagnosing and fixing a problem with carb cleaing etc.? Any guess would be helpful.

Thanks,

Sam
81 XJ650H Maxim Black

 

Yes, A&S BMW is the place. I used to go to them when they were out in Folsom, some 20 years ago. Last I remember, they were located on the north side of Sunrise Blvd, out toward the I-80 and Roseville. I've not had any dealings with the folks out that way in 7 years so please forgive me for the lack of details. The other place I remember is the Yamaha shop out off of Old Auburn Road, south of Madison Avenue. They were usually very helpful. Another place you might want to check out is the variety of motorcycle wrecking yards out in Rancho Cordova, there are about 5 of them. I've been able to talk to their mechanics for free most of the time (but when your buying their parts, they tend to be generous). Most shops are charging anywhere between $65 and $75 an hour for maintenance and trouble shooting. I would suggest that if you can afford the time, stick it out until you have the book and have finished your "homework" that I suggested earlier. You could save yourself a bunch of money by using this forum and your wits. Cleaning your fuel system is always a good idea. You just bought the bike. Do you have any idea of how the bike was cared for by the prior owner? Did you get receipts from them? I always flush the entire machine when I buy, even if they just did the work. I want to see the fluids for evidence of their care or neglect. How long was the bike sitting before you picked it up Sam? It could well be that there are some gummy deposits in the carbs and you simply need to clean it all out. A fresh tank of Techron 91 RON from Chevron could possibly set it all right. But as I suggested earlier, you need to know your base line. Is the compression any good? That is the first step. I don't know if you have tools or not but if you intend to be the maintainer for your machine, you will need to make an investment. Harbor Freight carries a very inexpensive compression tester that will give you a reasonable reading for under $10. There were three in the greater Sacramento area when I left, might be one or two more by now. You can do this yourself and save about $80 or more. I personally feel that doing your own work gives you a better sense of what shape the machine is in and a greater sense of "oneness" with it. I have had great service from every bike shop I have ever used (covering most of California) and I don't think you can go wrong there, but you lose out on a chance to bond with your steed. Let us know where you end up eh? Good luck!

 

Thanks for your great and helpful message, Robert.

Today, I drained the carbs. There was some gunk in there. Some liquid that did not dissolve in gas. Could be oil or something else. Gas looked clean. Changed the plug for cylinder #2. Put in some carb cleaner (Mystery). Tapped the #2 carb with a screw driver a bit.

Started it up and rode for about 10 miles in Elk Grove (started raining so came back). Ran just fine. Idle at about 1300. Brakes o.k. Rear brake not as strong. Lights o.k. Tires o.k. so far. Shifts fine so far...checked all the gears. Have learners permit so rode upto 50 mph and not on the freeway. (Question: why does the speedo go only upto 80 on this bike? It is a 650.)

Checked the #2 plug after coming back. It did not look black or sooty or oily. The second pipe, though, was still not as hot as the other three. Did not see any gas drip at the end of trip but that may be cause it may not have enough.

What do you think? This board is great for newbies like me.

Regards,

Sam
'81 XJ650H Maxim Black

 

Richard was the magic here Sam. His quickly pointing out the fuel system demonstrates a depth of knowledge I aspire to attain. Thank you Rich, I've much to learn it seems. Idle sounds just a touch high. I recall the idle being 950-1050 rpm. I'm with Rich on this. The "fluid" you drained might very well have been water (sure sounds like it), it doesn't like gas and will pool underneath it. This means that if it is in your fuel tank, guess what the first thing your carburetors sips? Flush that tank, pull and throughly clean those carbs and follow up with a tune up and sync. If your jets aren't clean, you could have a fuel mixture problem and that would lead to uneven heating of those head pipes. Have you visited the site Richard suggested? I love it, it is perfect for the beginning wrench and would give you a great basis in motorcycle mechanics. I spent two days soaking it all in two years back and it was inspirational. I occasionally visit it from time to time (bookmarked it right off the bat). What would we do without you Rich? About your speedo question, I've not the faintest idea why they did that but I have a hunch. Import tariffs can be higher for performance machines and around the time this bike was imported there was a big gas crunch on. I'm assuming that the idea was to psyc people into behaving themselves on the throttle if it didn't look like it could go faster. I think the factory did it to try and fool the DOT and the general public into thinking it was a lowly put-put. It is a very docile machine with very plesant handling character. I think this is one of the finest bikes I have ever ridden. I'm also of the opinion that this is a perfect first machine for a new rider because of it's character. It's got enough to get you out of trouble but handles easily and is very forgiving. I won't part with mine for love nor money. As far as cleaning the carbs, there is a favorite snake oil here at the forum I've yet to try, it's called Seafoam and is found in most boat shops and high end car parts retailers (NAPA, etc...). I have used Berrymanns B-12 Chemtool for my tune up for years. A quarter can to a full tank of premium from Chevron twice a year. Never had to clean carbs again. Get your tune up done and write back. I'm still curious as to why your pipes are heating up differently. Rob.

 

2 things were left out guys. 1. With the engine off, pull the fuel line off the petcock and see if fuel flows with the petcock in the on position. If it does then you need to rebuild the petcock. With the engine off fuel should only flow at the PRI setting. This or the float valve is your source of the rich mixture. When the mixture is rich the fuel doesn't burn fully. This leads to a cooler header pipe. Lean mixtures can do this too.
2. You can check the fuel heights and see if the #2 carb is high. I highly suggest since you have already pulled the carbs once and that is not a new procedure for you to order a rebuild kit for the carbs and at least replace the float valves. Even if the petcock is leaking the float valves should stop the excess flow of fuel which runs out of the airbox. A leaking petcock will only make a weak seating valve leak. The weak seat will either be the product of a bad valve or a high fuel setting holding it back from seating. To check the furl height simply slip a section of clear plastic tubing over the float bowl nipple and open the drain screw. Allow the tubing to fill while holding it straight up against the back of the carb. Where the fuel stops is the fuel level. It should + or - 1mm below the top of the carb bowl. Good thing is that both checks can be made without removing the carbs. Just make sure the bike is on the center stand and is level while doing the fuel height check. One other little point, the XJCD has an entire section of this with pics. No other manual does. Worth everybit of the $10.

 

Don't forget to have the petcock on prime when you do your float test, you'll need the fuel to continue to fill the bowl when you open the bowl drain in order to get a good reading. If you don't, the displaced fuel will not be replentished leading to a low float reading. Thanks for the back up Max! I'm going to get one of those XJCD's as soon as they are released!

 

Re: Need help with gas leak and one cylinder on Maxim 650 19

sakhan53, if you decide to take the carbs apart, make sure you check/replace the o-rings under the float valve seats (if your model has them). I had a similar but ongoing gas leak problem on my Seca five years ago (plus gas in my oil), and new o-rings were the solution.

 

You guys are tremendous...all of you. What a great bunch of folks working on such a pretty machine. I described the '81 Maxim as "pretty" to one of the mechanics here in Sacramento, and he smiled...seemed to agree. I know next to nothing about bikes (alhthough learning fast) so he must have thought me pretty silly

I am going to definitely get a copy of the CD now after hearing so many good things about it.

I am going to try the different techniques and let you guys know asap. Have been busy with some other things these few days.

One or two more questions: is there an easy way to get rid of minor rust spots (very few on this machine) from the painted surfaces. The chrome on this one is almost perfect. Also what kind of tires are best for this bike? How much do they cost and where do you buy them?

Again, thanks for the advice.

 

Alright, here you go. I use a Pasche Air Eraser (mini sand blaster) to touch up those little spots and touch-up using either PS1 Chassis Black or Case Black (depending on where the corrosion is) or Black Epoxy Appliance paint. On chrome, use #0000 grade steel wool to scrub it off and polish up the surface (don't forget to wax afterward to protect). For difficult spots, use Autosol (made in Germany, great stuff) or the domestic Muther's Mag polish. Tinfoil and vineger will work on chrome too (old but effective trick). I run Dunlop K491 SeriesII tires and get great life and handling out of them, usually 20,000 out of a rear and twice that on the front. They run about $110-120 each and should be available from just about anywhere they sell bike tires. They can even be purchased on-line but I would encourage you to support your local shop (keeps them around for when you need them!). Good luck and keep in touch, I might be up this summer if I move!