Something BIG let go on me--engine damage :(

....and she was running SOOOO sweet too :cry: .

'82 Maxim 750, 34000 mi.

Merging on to interstate the other day and at about 7000 rpm, something let go inside her and .....silence. Engine would turn over (way too easily...as if the plugs were out of it) but no banging or otherwise at that point.

Got it home, pulled the valve cover and side cover to turn it over manually. Even though it turned over just fine with the starter at the roadside, when I attempted to do so manually there IS something trying to hang up...doesn't want to be rotated past the TDC mark. My guess is that it swallowed a valve.

Question: Can the head be removed without taking the engine out of the bike? I'd like to see exactly what kind of mayhem lies inside before throwing in the towel.

Right now, chances are I will simply sell the bike as is or part it out...once I see what's gone on inside I'll decide what I want to do. The bike is otherwise in VG to excellent shape, but I'm not really wanting to put a huge amount of additional money in to it ... :cry:

Thanks, everyone.

Tim

 

put the engine on a bench and FIX IT!!! i dont know if the head can fit off in frame...i would guess yes.

assuming you had proper valve clearance before, check to see if there are any tight buckets. if you have a tight bucket, the valve is no longer holding it down. if you have .25" clearance...the valve is bent and remaining unseated.

can you see anything from the spark-plug holes?

how is the cam chain?

 

You can pull the head off in the frame.


MN

 

+1 Zookie400 ~ ~ what he said

You should be able to see all the valves thru the plug holes.
You're looking at buying a piston (?) a couple valves, some gaskets,
Make it better than it was !!

 

There's plenty of room to remove the Head without Pulling the Engine.

But, if you are going to have to "Get into it" further than doing Head work; its worth having the Engine out to be able to have the Engine on a Bench and not be bending-over and having Frame Members in the way.

Alternative Quick Fix:
http://cgi.ebay.com/ebaymotors/YAMAHA-X ... ccessories

 

Many thanks for the replies, gents. I'm out of town until Sunday eve, but I'll have a look at things then.

When I was on the roadside, I pulled plugs 1 and 4 and I could see the pistons and valves operating (engine was turning freely with the starter). 2 and 3 I didn't check as I intended to when I got it home.

Cam chain SEEMS fine. My first thought is that it may have somehow slipped a tooth and I wanted to rotate the engine manually, align the marks and see how that was, but now something inside the engine is hanging up and obviously forcing it would be dumb. I'll check the valve clearances as best I can given the limited amount of rotation available and maybe look at cyls 2 and 3thru the plug holes for some clues.

Since pulling the head can be done in frame, I'll be doing that anyway. If I decide to repair it and it involves the bottom end, I'll pull the headless engine out altogether. Once I see what's what, I'll decide whether to fix what I have, replace the engine altogether or sell the bike.

Rick, thanks for the link. I found another engine as well in Cleveland, but this one sounds waaayy better with that kind of mileage. I seem to recall reading that a 900 won't fit in this frame (assuming I could even find one) but can you confirm that for me?

I'll report back next week with what I find out. Thanks again everyone.

Tim

 

FINALLY got the head off: 4 bent intake valves. Pistons have a small mark but do not appear to have been damaged. Tons of carbon on the crowns, so something may be bad on them that I didn't see, however.

I assume that the cam chain jumped a tooth, but it seemed plenty tight after removing the valve cover. Not sure whether it's worth trying to replace the valves and rebuild the head or just replace the engine. Are valves even still available? Head gaskets? I want to look at the crank sprocket to see if it's been damaged somehow (kinda doubt it, but I want to be certain that the bottom end is OK if I decide to fix the head).

Needless to say, I'm also wondering HOW this might have happened as well. I WAS on it pretty good (7000 rpm and merging) but engine has NOT been making any funny sounds and I reset the chain tensioner last fall when checking the valve clearances.

Anyway, I'm hoping for suggestions on what to do next here. Thanks everyone.

Tim

 

Tim,

If 4 valves all failed at once I would probably check out a sprocket or cam issue!
There are valves aval @ around ~$150 for a set of four. Top end gaskets are ~$110-120 plus all the labor. Sprockets and new cam chain ~80 OR new cam(if thats the issue instead of sprocket) ~$200-300.
I have been shopping for simmilar items as I am pulling my head at this time.

Long story, if you can find a working replacment motor BUY IT!! Easier in the long run in my personal opinion

If you decided to pull head, make sure pistons are cleaned down to the aluminum

 

Hey tim. If I am not mistaken the valves from a xj650 ar the same as the 750. I have a motor from the bike I am parting out that I am thinking of stripping down. Not much interest in it at the moment. I would be happy to let you have dibs on 4 of the valves from it. Camshafts are also the same. Let me know...

 

I'm with those who will tell you NOT to put money into rehabbing that Engine.
If you were tach-ing 7-Grand and the Mill locked-up ... you can bet something else got torqued outta-shape. The question is ... what?

I'd sure like to know what happened to that Engine?

When you updated the situation saying the Chain was tight but you had bent Valves ... I started to think that you broke that Crank.
That would sure bring things to a halt immediately.

 

I'm sorry I simply Cannot get past the : "83 Maxim 34,000 miles
Ummm HOW is that possible??
That bike got ridden 1300 miles per year For 27!! years??
C'mon it's likely got 134,000 miles and it's Wayyy past it's sell by let alone fix it again, date

 

I dont know how it is in canada but in the usa people tend to get bikes and ride them for a few years and then forget about them. Thats how my 82 has only 4,000 miles. Oddly enough I have noticed that most used bikes for sale have around 22,000 miles. It doesnt matter if it is an '82,92,or 02. It kind of goes along with the ride for a few years and sell/forget about it scenario.

 

I saw something similar to this when I worked at a shop. Bike would turn over, but you could hear there was no compression, no spark

After pulling the valve cover (this was a virtually new zx6r) we found that apparently when someone adjusted the valves, or replaced a cam or something, they didn't tighten down the cam gear to the cam. It snapped the gear off and threw the chain off the crank. Not a pretty sight.

I'd say there was something with the chain. I'd say find another bike and use it as a donor, or maybe use this bike as the donor.

 

Thanks for a the replies guys. Right now I'm leaning toward a replacement engine. It sure has me stumped as to what could have caused this though. These engines have such a rep for being bullet proof, but any man made thing can break and I guess I drew a short straw on this one. Having said that, I've ridden this bike A LOT and learned a lot about both riding and fixing...it IS my first bike.

I guess I'll begin the process of removing the engine from the frame. Might attempt to do an autopsy on the bottom end later on. Still a possibility I may just part the bike out, too.

Thanks again guys.

Tim

 

Not uncommon at all.

These bikes get ridden, the shoved in a corner and forgotten about. Maybe pulled out again over the years, ridden a bit, and then forgotten again.

My '81 had 18,000 on it when I got it; it NEVER sat, but it was only ridden 300-500 miles in some seasons. The PO was putting on MAYBE 1K a season when he sold it.

My '83 has less than 8K on it; it had 7100 when I got it. It SAT. A LOT. It got put back on the road at one point for about 2-3 seasons, six or seven years ago, then back into a corner of the garage.

In the case of BOTH bikes, I have absolutely no reason to doubt the original odometers. Everything I found in going through them was consistent with the miles on the clock.

 

Fair enough.. I'm sure it is possible and a great discovery when it it's truth.

Although in the last 5 or so years EVERY single early 80's Bike I've seen (regardless of Brand ) has about 30,000 on the odo.

Universal coincidence or just fraud ??
Enough miles for it to be believable/saleable , but not enough to cause worn out worries in the mind of the prospective Buyers?
Gotta Love Humans.

 

I have to agree with Fitz. My 550 has less than 12,000 on it. It sat for some unknown number of years and, with half the year not suitable for riding and, since most of us don't ride to work regularly but rather go on pleasure rides on the weekend, around a thousand miles a year is pretty common.

I recently saw a 74 Honda 360 with less than 1,000 miles on it. Single guy I knew bought it for his nephews to ride when they visited the farm. When they grew up it sat in a machine shed for most of 30 years until he died and it was sold at auction for $400. Still kicking myself for letting it go that cheap.

 

I rescued my 83 Max from the PO. 9,000 Original Miles on it.

Theres around 23,000 on it today.
You can find Low-miles Bikes.

 

I found an 81 maxim 650 with 16,000 and a 79 KZ650 with 10,000 both are original and were an alternative mode of transportation to the owners.


Art

 

THE JURY HAS REACHED A VERDICT....

...and some of you will hate me for this, but I've decided to part out the bike.
I'll be posting more info on the sell, trade, swap, wanted forum soon. If anyone might be interested in the whole bike before I start breaking it up, feel free to contact me. Most of the bike is in very good to excellent condition, with a couple of exceptions (pitted chrome on header pipes and non stock pipes, for example).

Anyway, my thanks to everyone here for all the help and advice over the past 3+ years. Extra special thanks to Rick, whose detailed instructions were indispensable in last year's carb cleaning festival. I hope the remaining good parts on my bike will help keep some other bikes on the road where they belong.

Tim