New Maxim owner just can't get her started...

So I bought an '85 XJ750XN the other day that hasn't run in about five years. The owner said it had started running poorly (maybe bad gas) so he just put it in the back of the garage 5 years ago and lost interest amisdt all his other bikes.

I got a screaming deal on it and hope its worth it! Overall the bike is in very nice shape with 26,000 miles.

I've replaced the battery, oil, and plugs, and rebuilt the carbs thoroughly, unplugging a couple jets along the way.
So I put it all back together, hit the starter, and waited for it to pop but to no avail. It will crank all day long with not even a sputter... Damn.

I've got a nice fat spark on correctly gapped plugs. I've got new fuel mixed with a drop of seafoam. I've got sparkling carbs with the mixture screws turned out 2.5 times (900 degrees of rotation). I've got fuel in the bowls. I've got nice vaccum from the carbs and good strong exhaust pufts (though no compression tests yet.)

The only things I didn't do to the carbs were remove the choke assemblies or the main nozzlesthat the needle goes through (beacuse they were held in place by a pin and passed the visual inspection and blow through tests.

I comfort myself that even if I missed something tiny along the way, it would still run poorly. I can't get this bike to fire even for a split second with starting spray or a cap of cas in the cylinder.

What I've got is a bike that decorates my front yard.

What have I missed?

Please help, and thanks in advance!

 

i bet your having compression failure. If it doesnt even sputter with starting spray, your probably not able to compress the gas, nor would you be able to harness the power if you could get it to fire.

Bad rings are my bet, or cylinders are out of round.

 

I'm going to suggest that the rings on the pistons are sticking (this is predicated on the assumption that the motor was sound before it was parked), common with a parked and ignored bike. I've encountered it before. A shot of about a teaspoon of Marvel Mystery Oil down each cylinder and turn over by hand. Let it sit for a few hours (preferably overnight) and try a compression test the next day. If you have anything over 90 psi, you should be ok. Suck, squeeze, bang, blow. Hope the outcome isn't as dire as Brian sees it, but he may be right. Get that compression test out of the way before you spend more on it.

 

What I find strange is that it slowly failed for the PO. I wouldn't have expected dry rings from a regularily ridden bike. I suppose if the PO had lots of other bikes maybe it wasn't regularily ridden.

I would have said it is the pilot jets not being cleaned - but you said starting spray did nothing... so if that did nothing then I'd have to think it was something else.

Did you check the airbox doesn't have a squirels nest? (NOT KIDDING)

Otherwise - with a good spark (how'd you check that?) compression sounds more likely. Roberts oil idea is a good one - certainly no harm in doing it.

 

Thanks everybody. Good advice. Rest assured the main jets and airbox are clear. I checked the spark by groundling the plug on the side of the block. (oh, and by inevitably shocking myself of course!) Good current there!

The PO told some other assorted motors he had started running poorly at the same time and his deduction was bad gas.

I will certainly try some mystery oil in the cylinders and do a comp test asap.

How about valves? If compression is poor they might be an issue too. I've never delt with valves of this complexity and don't know where to start.

By the way, do you all find it necessary to use the choke to start this particular bike?

Thanks again guys.

 

My bike will kick over without the choke when cold, but itll sputter out after a few seconds. Its pretty much mandatory, when the engine is cold. If your going to do a compression test, do one before adding the oil to see how things go, if it fails the first time, drop about a teaspoon of oil in each cylinder crank it a few times, and then do the test again, if it passes it is almost definitly a ring seat issue. Of course the oilmight also unstick a ring which might very well solve the problem. give it a go, and let us know how things turn out!

P.S. dont be intimidated by the valves. It is basicly the same setup as in any other OHC setup. They seem tricky, but take your time, you can do it.

 

I would advise against the practice (I do it myself) of grounding the plug to the engine block. I've been told by a mechanic friend of mine that it's not a very good test of spark and that if you get the mixtures just wrong you can have the spark set off the fuel that is being pumped into the cylander...

What he said about the spark was that it is all fine and good that it fires nicely at 1 atmosphere, but it wasn't a very good measure of what it would do at a much higher preasure... he suggested using an inline spark tester...

After saying that - I've also checked I had a spark against the engine as no spark and weak spark are two different beasts to diagnose.

Still after saying all that - I don't think the spark is your problem as you say... I just wanted to throw this out there and see what the general concesses is here.

 

Well, I did set one car on fire one Christmas Eve a few years back doing just that. Lessons learned and the car was not harmed (don't know how we pulled that one off, had the extinguisher handy as always). I have not had an issue with the spark test grounding the sparkplug. I just pull the plug back toward the carb side of the head. There is something to be said about spark quality under pressure but to determine if the ignition is good, one needn't have the high dollar color tune (although first cheap one falls in front of me will be scooped up). I would simply suggest to be mindful of where the fuel mixture is in relation to where the spark will be generated (provided the machine can produce one). I'm going to piggyback on Woot, your compression test will determine your issue, you've already eliminated your ignition system. Get that compression test done! I'm eager to hear the results.

 

Hey XJRook;
I have to agree with woot and Robert, I don't think it's spark related either.
I would do the compression test first. Then I would pull the chokes(fuel enrichment valves) that you said you didn't take apart in your original rebuild. They actually allow more fuel for startup, and may be clogged.
Did you clean the starter circuit jets really good, that's the small hole in the fuel bowls?
Did you set the fuel level in the bowls using the clear tube method? 3mm plus or minis 1mm down from the carb body.
Just my 2 cents
Good luck

 

I've got some marvels oil in the cylinders now, soaking since yesterday. Perhaps too much... I took the plugs out this morning trying to dry the excess before I try and turn her over. Its a great idea. I have a good feeling about it. I thought I'd just try to get it to fire before I go buy a comp tester.

Starter circut jets clean as a whistle.

No I havn't set the float level in the carbs... you say 3mm down from the gasket where the float bolts to the body of the carb?

Any hints on cleaning out the spark plug holes? i've got a little bit of crap in there and I worry about knocking it into the cylinder.

 

Compressed air is probably your best bet for cleaning around the plugs.

The very bottom edge of the carb body. 3mm + or- 1mm

 

Compressed air for the loose stuff is the best method for an initial clearing. I use technical cotton swabs (8" long) and what ever type of cleaner you have at hand (alcohol, carb cleaner, etc...) for the finishing touches.

 

Less than 50 psi all around with the throttle wide open... sweet.

I'll drop a little oil in the cylinders and see what happens. Didn't have any handy at the time, believe it or not.

If it is the rings... are there any good products to try besides marvels or seafoam? How about ATF fluid?

 

Berrymann's Chemtool, Mom's spit (everyone knows mom spit cleans anything). Best I can do, Marvel and Seafoam are the only other products I know of.

 

A bit of oil in the cylinders didn't seem to make a difference at all. Can you believe I've got comp as low a 20psi on cylinder #4 ?! So sad...
The previous owner told me he has trouble starting the bike cold, but it ran alright warmed up. Makes sense that the heat would help seal the stuck rings.

Looks like I'll be replacing the rings and maybe boring the cylinders depending on what I find.

I suppose I should do a leakdown test before tearing her apart, just to be sure.

Thanks for all your help, everybody. I'll keep you posted. -jon

 

Just for sh**s and giggles I would also check valve clearances before I opened her up. Might have a valve sticking.

Just a thought...

 

How? I've never delt with overhead cams before. I'm a two-stoke man, man.

I suppose if I take off the top of the heads it would all be plain as day... though a leakdown test should pinpoint the prob for me.

 

No improvement on a wet test suggests valve issues Rook. Pop your valve cover and ensure the cams are rotating. If your cam chain fell out or the drive gear bolts fell out, your spinning your wheels. Let us know what you find.

 

Fine idea. I'm in the process of moving, but I'll get to it asap. Sure would be nice not to have to replace those rings!

Because it was easy to do, I've had the cylinders filled with atf for this past week while I was on vacation. Might help a bit, can't hurt...

 

Sorry I haven't checked this topic sooner...

I just finished reconditioning my Maxim X. When I first got it, it had been sitting for 5 years. I did a compression test before I did anything else, and two of my cylinders were at 40psi, and the others were at 90.

I soaked them in oil, but I don't remember if that helped, I don't think it did.

Long story short, after I got it fired up, compression came right back up to 150.

My conclusion would be, don't tear down the engine unless you have exhausted EVERY other option! I was VERY tempted to do this, but I am so glad that I didn't.

I would be checking electrical problems and carb problems... Are you sure that you have an idle speed set so that it has a chance to fire up? This took a lot of playing around for me.

Also - are you sure your battery is good? I had a bad battery, and mine would crank, but not fire.

Lastly, don't feel bad about starter fluid. I know it is bad to run an engine on this, but if you have to do it to get it started, do it!

What I did, is I ran it on starter fluid for about 2 minutes! It was crazy, but while I did that, I was able to get the idle speed right, and it helped to cycle the carbs a bit.

After this, I think that parts of the engine started to loosen up, and the rest is history! After about two weeks now, she is purring like a kitten, and roaring when she is asked!

So, keep playing with the starter fluid to loosen up those rings. Also, I sprayed sea foam in the intake, and that knocked carbon off of the valves, which also helped compression. I know it worked because the exhaust made me sick! :lol:

 

ATF in the cylinders is a good idea, just be sure to drain it and refill with the correct lube before you go wild on it. Hope the move is as painless as one can be (meaning it is painful but hopefully the pain is short lived).

 

Thanks for the tips everyone. Richard, your story was welcome! Hope I have such good luck too.

Carbs are whistle clean. Don't know the proper idle setting... Played with it a bit but it didn't seem to help.
Battery is strong and the spark plugs are-a-sparkin!

I'm no stranger to startin fluid. To be honest the smell gets me a little excited! My girlfriend thinks I'm nuts. Anyway, it didn't seem to work last time I tried and I used plenty. I think my compression is so bad it's a lost cause.

On a brighter note, before I left on vacation and filled the cylinders with atf, I was advised to pop start it because it will spin the engine faster, an about halfway down the hill it fired! One little pop and a little exhaust smoke was all I got, but it made my day.

 

Hope springs eternal! There may well be life left in that motor after all. Keep trying!

 

Couple of tips from someone who just did the exact same thing.

I had oil in my bores of my XS as well to loosen things up and bump compression. Trouble was, when I tried to start her the oil just covered the plugs and killed any spark.

Two options to try
1, put a teaspoon of gas down each plug hole and replace the plugs. This dilutes the oil a little and makes it a bit more combustible.

2, and this is what worked for me, Wash the plugs clean with petrol and put back in the bike wet. Squirt of starter fluid in each carb and she flew into life albeit a tad smokey.

To be honest, I didn't have starter fluid so I used a tiny squirt of carb cleaner. Man the label on that tin that says flammable should be much larger. :wink:

Also doesn't hurt to pull in the clutch when cranking as it will reduce the load on the starter.

These baby's are pigs to start sometimes if the carbs have been stripped. Not unusual to need some extra "squirt" to fire them up, but once alive a good sync and tune should see reliable life in her every day.

Keep at it, She'll go, I can feel it in my bones. :lol:

 

i just changed out the head gasket on my two stroke bike...saw you were a two stroke man :wink: and it called for a lightly greased gasket...lightly greased it was but all the excess went into the cylinder and i went through two days of hell befotre i finally got her going and just ran her for three hours to burn off all the grease, now she goes over on the first kick!...just spreading some hope

mike
the dopeless hope dealer