Thoughts on what to do.

Hello,
I've just recently purchased a 82 xj650 maxim. When I picked it up previous owner told me everything that he did to it(cleaned carbs, tune up) and that these bikes are cold natured. I figured it was a carb/fuel issue. After getting it home and digging into it I found this bike has had a hard 34,000. She only has 60psi of compression on all cylinder, wet is about 90. I've tried soaking rings with different brands of (snake oil). Also notices that it has a weak spark. Coils ohm good on both sides. They are getting 12 volts while cranking. I checked valves and they are within spec (intakes .005 exhaust .007) If its above 50 degrees outside she starts right up with choke and runs if the fuel petcock is on PRIME. if its cold she cranks and cranks or if I turn fuel petcock to on. Looking online its real easy to sink 100's of $$ in these obsolete parts if I were to rebuild. What do you suppose would happen if I just ran it like this? Also what I think is weird is despite low compression I get no crankcase pressure at vent tube? Thanks

 

Start here:
http://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/

Realize that the previous owner may or may not have refurbished the carbs when he 'cleaned' them. After you read the Information Overload reconsider if you want to invest the time and money to bring this great bike back to a safe and reliable condition.
If you answer yes, then know that all you 'obsolete' parts are available here from XJ4Ever plus all the advice/ help you need lies here within this great community of XJ enthusiast.

 

TCI ignition systems throw a spark that looks weak compared to a CDI ignition system. It's not weak, just different. Make sure that the plug caps themselves are within spec (you migh even take the resistors out and check for corrosion), and that the ends of the plug wires are corrosion free (they can be cut back a bit until you get to clean wire).

Read that link up above me.

Are you checking the compression with the engine warm, and the throttle wide open? If not then do that and you'll see the numbers come up.
If so, then try a different compression gauge. We've had more than a few people find that their gauge is faulty.

Just cleaning 30 year old carbs won't do. The throttle shaft seals and other rubber parts (aside from the diaphragms) dry up and start leaking. I'll wager two things:
1. The previous owner didn't do a thorough job of cleaning the carbs (he likely missed the enrichment jets in the float bowls).
2. If the throttle shaft seals aren't leaking vacuum now, they will be soon.

IN THE CHURCH OF CLEAN

Read ^^that one^^ as well.

As for the parts costs: In the end you'll still spend less than you will buying a motorcycle that needs no work at all (and they all need work, even new ones).

 

Thanks fellas, I will look at the pages you sited. I kinda suspected the ignition wouldn't be as strong as modern ignition. Can I pull the head and cylinder assembly with engine in bike? I wanna fix her right if it makes sense but I'm eager to ride her also.

 

Check your valve clearances first---- if they're out of spec, get them in spec then recheck the compression.

Also, if your compression tester is a Harbor Freight variety ( or of similar ilk), get a real one and test again.

 

I missed this on my first read through. You didn't specify the units for your measurement.
If you used metric, either you put in an extra 0, or the clearances are a lot too tight.
If you used inches, you're good, but both will need to be checked again fairly soon (I'd say 2,500 miles instead of the usual 5,000).

 

AND...... if you used the wrong manual, you may have used the wrong measurements to begin with.....

 

Ok I need some more guidance. After removing and disassembling my engine I found cylinder is worn out/ pitted. Several bolts broken in head and it's also unusable. Ruined it trying to extract intake/ exhaust bolts that broke. I'm thinking it will be more costly to repair than to just replace. This is a 1982 650 YICS. I've found several 80-81 non YICS good engines. Will this engine fit in my frame. Also will my carbs run this engine properly without any mods. Are there any advantages to YICS vs non. Thanks

 

I'm in central ny, I have a few extra engines.....

 

A non-YICS engine will fit.
YICS has a fuel economy advantage, and a slight power advantage. Given the small tank that the 650 max has, you want the YICS engine in order to get as much range as you can.

 

There are intake boot differences, and some minor carb differences.... there are internal engine/transmission differences,etc--

 

And wiring differences, and ignition system differences....

Point is, you want a YICS engine for the ease of swapping it.

 

Ok you've convinced me that I need a YICS. Are these rare engines I'm not finding my parts on eBay.

 

Not at all… There's a gazillion of them around

 

I guess I just don't know were to look.
Can you point me in that direction. Tried eBay.Starting to feel depressed I got a $900 piece of scrap at this point. Doesn't help that I can't leave well enough alone. I should have just changed oil and rode it as is. The inside of this engine tells me for certain she had a hard life. Intake cam is scared from low oil. I'm afraid to take pan off and look at main/rods. Pistons have enough carbon on them to make a bag of charcoal. It's sad that it's been neglected. I really like the bike so i don't want to part and frankly in too deep to stop.

 

Ebay:

370220212167

Not mine, not related......

 

Does it have to be a engine from a Maxim or will engine from a seca work.
Hogfiddles,
Do you have a good YICS 650 that you would part with.
I guess I'm gun shy now with my situation. In the bike world what is considered high miles for a used engine.

 

You could use a 750 engine and rejet carbs

 

A Seca engine will fit, but it's solidly mounted, and it will need to have the shift mechanism swapped.

High miles for a used XJ engine? Well over 100K.

 

Thanks for info guys, I'm going to stick with what Yamaha gave her and perhaps *upgrade her later. Thanks to hogfiddles for turning me onto a possible new engine. I've got a inquiry out with questions too seller.