Maxim-X low compression

so i did a compression test on the bike to try and diagnose the no-start
results dry : 60-60-60-90
results wet: 70-70-65-95

so not much difference there. what i did notice is that while cranking, the vacuum line from the 2nd cylinder that goes to the petcock was moving. so i put my finger on it and low and behold it is pressurizing.

so now i have a direction to point at : the valves. since i do not have a manual (gonna get the xjcd asap) i wanna know the procedure for checking valve clearances and the specs for the clearances if anyone is up to it.

if ya'll just want to tell me to wait for the cd's go ahead, i won't take offence, just want to get the bike running and take one ride on it before the snow falls if possible

 

I thought it said in your original post that is was in running condition? So the guy bs'd ya? that sucks. How many miles on the bike? Yamaha says they don't need to be checked til 26000 miles or so. Did you ever ask the guy about the engine and why it is not black??

 

he said he had it running, but it was running poor until after 8-10 min of riding, then it would take off. doesn't really matter that much to me. all of my bikes i have bought have been no runners and it didn't take me much to get them running.

odo says about 45000km (~28000miles), so valves probably need to be checked.

as for the lack of black on the jugs, didn't ask. there is some bits of paint a near the top of the jugs, but not much. it isn't the first one i've seen with the jugs not being black tho.

 

The valves on the X are the biggest PIA to check and adjust but it sounds like you at least check. They are completely different from the airhead and you have (20) of them to do!

Numbers that low, I would like to see you pull the head (but that's just me)...the damn head gasket is like $45 or something like that.

If they have zero clearance there is a chance that the seats (or valves) are messed up.
AND getting the valve cover off without screwing up the gasket is no picnic either.

This may sound silly, but it doesn't take that much to get the engine out if you have the right tools and space.
Adjusting the valves on the bench was tough enough for me, I can't even imagine trying it in the frame.

 

Those number look like you didn't do the Test right!

All the Plugs out?
Fully charged-up Battery?
Throttles held Wide Open during the Test?

Run another test if you forgot to do anything.
Numbers that low wouldn't be good enough to get the bike to run.

 

Battery : good
Plugs : out
Throttle : wide open

If I can source a narrow-bladed or tapered-bladed feeler gauge locally, I'll be right on checking the valve clearances and doing pads if needed. Then if needed I'll pull the head and do some valve lapping or other work if required. If I need to pull the engine, I'll have to finish cleaning my garage first. It is a pig sty at the moment I'm afraid to say, but that is what happens when you play with old bikes.

In the mean time, I have the cylinders soaking in "farm fresh" cleaner. I'll probably drain all the oil tonite and top the cylinders up leaving the drain plug out.

I don't think the XJCD can get here fast enough. I guess I should have sent away for it before I picked up the bike. There was no way I was gonna pass on this bike anyway.


as a side note, one could say that I only paid 300 for the bike and 200 for a brand new tire to replace the bald one on the rear. I am one that prefers to do all the work myself and have no issue with buying parts (tho sometimes it is best if the wife doesn't know what the parts cost :wink: ).

 

What kind of tire did you buy for $200 dollars?

 

I didn't look too closely, just saw the receipt for it. Tires in general are overpriced here, especially motorcycle tires. I'm kinda lucky my local Yamaha dealer only charges me a couple bucks above cost. It is a shame that the sizes I need aren't ever stocked.

 

Just to bump to the top and give an update.

I managed to get the valve shims done and everything buttoned up.
put in the battery, and it didn't even crank over 3 times before she fired up and was purring like a kitten.

I am looking forward to riding the bike, but am expecting that i need to be cautious due to the power of the bike compared to my poorly tuned other bikes.

 

I'm curious were your valves too loose or too tight? Did you redo the compression test? Those numbers you have are real low - my 650 spec is 156 I think

 

The valves were all very tight, most of the intakes I had to go and trade the shims I got because there still wasn't enough clearance (all intakes I couldn't get a single feeler under)

I haven't done a compression test yet, probably won't until I heat cycle everything a couple times.

 

Yea, the turn-around time for the US-based fellow is pretty slow. It's reliable, but just not quick for folks like you and me that are in the middle of wrenching on a newly acquired bike and want to have the manual in hand ASAP!

The compression test results seem kind of strange to me as well. If that last cylinder also read low, I would say timing issue. Just seems strange that those first three cylinders are consistenly low...

 

Glad to hear you got her fired up. You won't have to be too carefull they do have decent power as long as you are going straight give er' be careful the first few times if you are getting into it from first to second mine will lift the front wheel a bit if I am not careful.

 

It should only take you about 45-Minutes to eyeball the Timing.
I'd say the bike was Timed right.
I doubt it would even start or there would be much more serious matters to deal with if it weren't.

 

Almost everything works perfectly. Took it for a quick little run where I found the second thing that still doesn't work. The first was the horns that kinda work in a sickly kind of way, second is the speedometer which I tracked down to the drive unit at the tire. It seems pretty seized up. Just add one more thing to the list of not-truths from the PO.

 

On the back of the horn(s) there should be a screw w/locknut on it for adjustment. Adjust it, and that should make it sound less sickly!

 

Man I wish I had my camera the other night. My horns worked then got sickly then nothing. Well me being me I took them off and apart. One bolt takes them off unhook the two wires and take them to the bench. There are 5 or 6 phillips screws on the back I took them out and with some 600 grit wet dry paper(dry) I cleaned up the contacts that after 23 years were a bit burnt. Reassembled loosened the locknut and adjusted them for the loudest cleanest sound. It helps to have a friend hold down the horn button but you can just as easily zip tie or tape it down and just use the ign. switch to cut it off and on. Make sure you retest when you tighten the locknut or tighten it with it on so you end up with the best sound. One could just as easily only adjust the screw on the back but I wanted to see what was in there and once I seen I wanted to clean the contacts. THe whole process took under ten minutes.

 

I've got a Maxim-X and the best I can say for the OEM horns is, when they work, the best you get is a "squeak." I plan on replacing mine with something much louder...it's on my list of things to do but hasn't risen to the top.