Compression between 115 and 120

I am about to undertake a complete restoration of an '85 XJ700 Maxim that was given to me by my dad back in '01. The bike ran (with numerous quirks) when it was given to me with just over 33k miles on the odometer. I know it had carb issues and it didn't run great. However, the bike has been sitting (garage kept thank goodness) since at least '02. My original plan was to get the bike running before I started the tear down but another forum member suggested that I do a compression test, and if that turned out well, begin the rebuild. I picked up a new battery yesterday and a compression tester and tested this morning. The compression ranged from 115 to just over 120 for all four cylinders. Is it safe to say the bike should run after the restoration or should I consider tearing the motor down as well? This is an important question since the plan is to sink a bunch of $$ into replacing all safety components, carb cleaning/rebuild, cleaning everything, new paint. Every part of this bike will be touched (except the seat which I had recovered back in '01) and reassembled over the next 6 months. Parts that are to be replaced will be new tires, brake pads, brake lines, fork seals, wheel bearings, gaskets and new stock tank (if I can find one within budget). By the time I finish I want this bike to be like new but with my vision for aesthetic appeal. Looking forward to any advise on the rebuild or suggestions on where I can find a good tank for a reasonable price near South GA/North FL.

 

The numbers seem a tad low but they are consistent, which is good. I assume this was done dry. Put a little oil in each cylinder and try it again. Let us know what pressures you get the second time.

 

I did find the service manual online this afternoon and saw where it stated that a psi of 128 is considered the minimum. I took your advice and dribbled a little oil in the chambers and retook the compression test. I got 145, 150, 158, 160. I may have dribbled a little more oil in chambers 3 and 4 since the bike was on it's side stand which made the dribbling a little easier. So I am assuming I should plan on installing new rings while I have the engine removed? Anything else I should plan on doing?

 

I think you just had a case of dry, sticking rings.....the oil helped loosen them back up a bit, and as you run it it will come back as things settle back in. Personally, I wouldn't bother going into the cylinders just for the rings. If you're already going in, then that's a different ballgame. I suggest you do a valve shim clearance check, a complete carb overhaul, sync/colortune, brakes, safety stuff, tires, and while you're at it you may as well do a fusebox upgrade (yeah....coming from a guy who still runs original fuseboxes on all of his bikes).....and tires.

That will get to a safe, reliable point where you can do the rest as you're riding, too......

dave

 

Thanks for the input. I wasn't planing on going into the motor unless absolutely necessary since I know first hand the bike ran when it was parked. All the safety stuff will be replaced but I hadn't thought of upgrading the fuse box. I'll have to think on that one and see how the budget works out.

 

the fuse box is cheap.. 7-14 bucks depending on what u buy. new connectors. if you are not changing the harness it is pretty straight forward.

 

Good thing it doesn't need rings (hopefully)......they're un-obtanium (at least, if it's an air-cooled model).

XJ700 models don't really need a fusebox upgrade, as they already use the blade-style fuses (their fusebox is under the gauge warning lights). However, they do have a separate MAIN FUSE (under the front seat, near the battery) which still uses an old-timey glass fuse, and it could be upgraded, but it's not as big a deal as the "other" XJ models since there are no fuseholder "clips" to age and brake; the main fuse is enclosed in a waterproof fuseholder that uses spring-loaded contacts.


We should have a good used tank available, drop us an e-mail for more details.

 

Thanks for the advice everyone. Chacal pm sent.

 

tabaka, if you ever find yourself in Valdosta let know. I'd love to see your bike and get some free advice. I hope to start tearing my bike down this week.

 

>>>> So, if an XJ700N needs rings, it becomes a parts engine? Bummer.

Well, you can always have piston rings custom-made, I recall one fellow having a set made for his airhead model a few years ago by some place in Arizona. NOT CHEAP. But, do-able, when push comes to shove.........

 

Well that blows, guess I need to hang onto the pistons and rings from my parts engine.

 

Never a bad idea..........!

 

Can't you guys get rings made over there?

 

Yes but it ain't cheap.

 

If anybody is interested in going in on getting a batch of rings made up please email me at metrobikerparts@gmail.com

I need a set for my customer's bike, and I wouldn't mind having a few additional sets on hand to sell on ebay or wherever, but I believe that there are usually quite large minimum orders to have rings manufactured.

If I can get a few people to go in on it with me perhaps we can make this possible. If we get a big enough batch made we may even be able to re-sell them individually at a high enough price to make back the money.

 

Talk to Len----