She's gutless...

My 1980 XJ650 maxim is giving me troubles. Canadian Vehicle Identification Number is 4h8 000718. picked it up from a guy a while ago and finally got it started and idling well. The carbs are synchronized and it purrs like a kitten.

But it's completely gutless, especially on the low end. It does not sputter. Tire pressure is good. Engine is getting gas.

Things that have happened to the bike that could potentially cause this:

- Flooded the engine because of bad petcock (but changed the oil and spark plugs)

- It came with 4 into 2 exhaust from an xj 750 and I think stock it's 4 into 1 exhaust.

- Messed around with the clutch cable. It seems to be functioning well now, although I can't be sure.

- Ran questionable gas through the carb resulting in it having to be removed and cleaned out. A complete carb job was done recently. Now filled with premium.

- Third cylinder has oil on the spark plug. All other plugs quickly get carbon buildup.

Any ideas?

Thanks all!

Aaron.

 

Have you done a compression test yet?

 

I'm pretty new at this. How do I do a compression test?

 

You'll need a compression gauge with an adaptor that matches your spark plug threads. You may be able to rent or borrow one from an auto supply. Or you can buy one for around $20-$30 if I remember right.

Warm her up, pull all of the plugs, disconnect your TCI, and go from plug to plug getting a psi reading. Make sure that when you turn it over you open the throttle all the way.

 

So if the compression is no good, how do I adjust?

 

If compression is low, put a little oil in each cylinder. If it bumps up, then rings are the likely culprit. If not, then valves are the suspect.

 

Compression will give you an idea of the health of your engine, After that you can tune. If it is gutless are you sure all 4 cylinders are running? The original exhaust is 4 to 2 with a crossover chamber.

 

Ah, I have a wizard and a red liner on my side. Cheers Bill. Also thanks to Joe.

Firstly, what is a TCI and how do I disconnect?

I'm pretty sure all four cylinders are running because I synchronized the carbs and all four needles held at about 14-15 when I was idling at 1500 rpm. Wouldn't it be impossible to do that if the valves were out? Or does that mean I may have adjusted the carbs to bad valves? What does that do?

The third cylinder was coughing when I adjusted the carbs but it seems to have stopped doing that. There was an exhaust leak on that cylinder that I fixed. The third spark plug has oil on it.

I don't have a compression gauge and I can't get one for a day or two because I live out in the sticks. An hour ago I dumped a bit of oil into the cylinders. There was no noticeable change to the sound the engine made and it didn't run any better than before.

When I said "purrs like a kitten" in the original post, I guess I should have said purrs like a very sick kitten that makes a metallic clinking sound.

So it was a 4 into 2 with crossover. Now I'm going 4 into 2. Does that make a big difference? Would that cause a significant power loss?

Thanks again.

 

Hi apato632

Before you do a synch, you'll need to check the valve clearances. If the clearances are out, you won't get an accurate synch. There are "how to's" on the site here.

The TCI is the black box also called "igniter". Mine is under the seat but some might be behind a side cover. It has two plastic block connectors which need to be unplugged to do the compression test otherwise you might damage it when the spark plug leads aren't grounded when disconnected for the test.

One check I did on my XJ when she was running poorly was to check the float heights in the carbs. All mine were too low and after I adjusted those, it made a huge difference. Whilst (if) you're inside the carbs, clean them again.

For the comp test, a teaspoon of oil in the cylinders won't make it "run any better", it is to see where (if any) the loss of compression is arising from as Joe says.

Check your valves and re-synch, read the compression on each cylinder and see what the result is.

 

Great, thanks.

I've tidied up the carbs again. Adjusting float heights is done by changing the tabs that hold the needles? Are you sure that's necessary/a likely cause?

 

That's correct - bending the tang slightly will alter the float heights. May or may not be your cause but it is a very worthwhile check, as I found out.

 

This may sound crazy but check your spark plug gap!

 

bpr7es is the plug type. They come pre-gapped from NGK, otherwise all my bikes are running on the wrong gap.

 

As far as I know - pre-gapped is just a rough guess.

Every application has a specific gap needed.

 

I would not trust the factory gap. Also those are resistor plugs. You would want resistor plugs or resistor caps not both. Check your plug caps - if they are resistor caps they should say so (5k or 10 on them).

 

BP7ES is what you should be getting your hands on. Non-resistor type since your spark plug boots have a resistor installed already.
Get those spark plugs gapped swiftly. NEVER trust a plug gap out of the box EVER! 0.028-0.032" torqued to 11-14 ft/lbs and you are good to go. You ought to use a smear of anti-seize on the threads (a drop or two of engine oil will suffice in the absence of anti-seize).
You should also consider having a set of spares on hand (cheap enough for a set, don't know why anyone wouldn't).

 

I've been told to go closer to the .028 instead of the .032, is this true?

 

yes.... as they wear the gap increases slightly up to .032 where it starts to exhibit problems

 

I had the same problem but worse the bike would run great without a load but when you put a load on it it would almost die and had no power.
It was the spark plug gap!

 

WOW. Will have to try this out.

 

Jeez, I wish I'd read this before I got elbows deep into valve measurements. Oh well. I'll have them up shortly. My project got rained out before dinner.

 

The proper gap is listed on the "tune-up" sticker that is inside your frame side cover (could be either side).

The factory specifies proper settings, clearances, torque values, and service procedures for a reason, mostly having to do with marketing puffery and wanting people to mess things up when servicing their bikes, but every once in a while they slip in----perhaps by mistake?----some accurate information like this!

 

OK, here's the measurements on the valve adjustments.

Are they out? What do I do now? Does it seem like valves were the problem?

Thanks again all. I'm going to go out to Canadian Tire and buy a spark plug gapper right now.

Numbers include imperial and metric measurements.

Front
1 y 270, .15mm/.006 NO, .13mm/.005mmYES
2 y 275, .15mm/.006 NO, .13mm/.005mmYES
3 y 270, . 18mm/.007 NO.15mm/.006 YES
4 Y 275, .15mm/.006 NO, .13mm/.005mmYES

Back
1y270, .1mm/ .004 NO, .08mm/.003 YES
2 y265, .0025/.06mmNO, .002/.05mm YES
3 y 280, .002/.05mm NO, .0015/.04mmYES(barely fits)
4 y 280 .002/.05mm NO, .0015/.04mmYES(barely)

 

By "FRONT" do you mean the EXHAUST valves (meaning, towards the forward/front of the head)?

 

Also, by "YES" do you mean that is what thickness feeler gauge will fit thru the gap?

 

Yes to both. Please excuse my newbie code.

 

Okay, then ALL of your clearances are way too tight, which is common on these bikes....as the valvetrain components wear, the clearances get tighter, not looser.


The specified range of acceptable clearances is:

.11 - .15mm on the intake valves
.16 - .20mm on the exhaust valves.

Valves that are too tight make a bike perform poorly, reduce power, and make it impossible to accurately perform any other (fuel system) adjustments or diagnoses.

Tight exhaust valves, especially, are very prone to warping of the valve face and seat, which leads to very expensive repairs!

You really need to resolve these issues as a first step in your tuning process. Save the money for the spark plug gap-setting tool; that is the least of your worries!

 

So sparks were gapped to .30. I re-gapped them tighter to .28 and yes I have spares

Thanks to chacal, dpawl31, jamings67 and others above.

My understanding is there is some sort of chart I need to follow.

What replacement shims would you recommend for the following measurements? To these numbers make sense?

Front / exhaust (Range .016 - .020mm on the exhaust valves.)
1 y 270, .15mm/.006 NO fit, .13mm/.005 YES fit : GO TO ?
2 y 275, .15mm/.006 NO, .13mm/.005 YES : GO TO ?
3 y 270, . 18mm/.007 NO.15mm/.006 YES :GO TO ?
4 Y 275, .15mm/.006 NO, .13mm/.005 YES GO TO ?

Back intake (.011 - .015mm on the intake valves)
1y270, .1mm/ .004 NO, .08mm/.003 YES : GO TO ?
2 y265, .0025/.06mmNO, .002mm/.05 YES : GO TO ?
3 y 280, .002/.05mm NO, .0015/.04 YES(barely fits) : GO TO ?
4 y 280 .002/.05mm NO, .0015/.04 YES(barely) : GO TO ?

Thanks !!!

 

Would it be too much to ask for a degree of consistency from you, Len, one minute you proclaim that the Yamaha staff are omnipotent & in the next breath you say that their word should be taken with a pinch of the proverbial. :?

 

Now you have established you need to adjust those valve clearances, do a search here and there is a chart that some kind soul (the name slips my mind) posted showing what shims are needed in an easy to read format. I just used it but it is on my other laptop which has just gone t*ts up and needs my backup image to be loaded.

It is there to be found though and it will tell you which shims you need quickly and easily.

 

Front / exhaust (Range .16 - .20mm on the exhaust valves.)
1 y 270, .15mm/.006 NO fit, .13mm/.005 YES fit :
GO TO: 2.65

2 y 275, .15mm/.006 NO, .13mm/.005 YES :
GO TO: 2.70

3 y 270, . 18mm/.007 NO.15mm/.006 YES :
GO TO: 2.65

4 Y 275, .15mm/.006 NO, .13mm/.005 YES
GO TO: 2.70


Back intake (.11 - .15mm on the intake valves)
1y270, .1mm/ .004 NO, .08mm/.003 YES :
GO TO: 2.65

2 y265, .0025/.06mmNO, .002mm/.05 YES :
GO TO: I assume that the .05 measurement above
is actually the mm size! 2.55

3 y 280, .002/.05mm NO, .0015/.04 YES(barely fits):
GO TO: 2.70

4 y 280 .002/.05mm NO, .0015/.04 YES(barely) :
GO TO: 2.70



Just so you understand the process in the future, let's go over it one step at a time:

We'll use this valve as an example:
2 y 275, .15mm/.006 NO, .13mm/.005 YES :

Front / exhaust (Range .16 - .20mm on the exhaust valves.)
#2 cylinder
Y275 shim currently installed
measured clearance: .15mm/.006" NO, .13mm/.005" YES


a) your measured clearance is .13mm.
b) the specified clearance range that you're shooting for is .16 - .20mm.
c) your clearance is SMALLER than it needs to be, since .13 is less than the minimum specified clearance of .16mm.
d) which means you want to obtain MORE clearance.
e) which means that the shim pad must be THINNER. A thinner pad will increase the amount of free space between the pad and the cam lobe.
f) how much thinner? Well, you are .03mm too tight currently (.16mm - .13mm), so you need at least a .03mm thinner pad.
g) pads only are available come in increments of .05mm, i.e. 2.50mm, 2.55mm, 2.60mm, etc.
h) so the use of a .05mm thinner pad will get you .05mm MORE clearance.
i) since your currently installed pad is a 2.75mm pad, and since they only are available in .05mm interval sizes, then the next thinner size will be a 2.70mm pad.
j) once you install the 2.70mm pad, and rotate the engine over once or twice to properly seat the shim pad in the bucket, and re-measure your clearance, it should be equal to your originally measured clearance of .13mm, plus the additional .05mm from the substitution of the .05mm thinner pad, which equals .18mm.......and which is now within the specified range of .16 - .20mm.


The most confusing aspect of it is that if you want to "add" (INCREASE) the clearance gap, you have to use a numerically "smaller" (THINNER) pad, which is sort of counter-intuitive when you read about. Once you "think it through", it makes perfect sense, just like most or almost all of Yamaha's specified procedures, torque values, settings, etc.

 

Huh.. I wonder if that means my intake valves are off.. 1 3 and 4 intake are at .005 and 2 is .006

 

Apato - http://xjbikes.com/Forums/viewtopic/t=14827.html

That is Fitz's valve guide.
The chart is on there. Works for every XJ except X models and the 1100.

Len, honestly glad you didn't respond to Wiz's comment.
I just don't get why he has to be such a crab.

I trust whatever you say, with good merit.
I can see where he might be coming from, but it all honestly certain things you SHOULD trust Yamaha's techs, and some things they are just plain wrong and scandalous.

 

.005 inches = .1271mm
.006 inches = .1525mm

Intake clearance ranges are specified by the Yamaha engineers via their "storybook" service manuals and other published literature---and which should be dis-regarded in this specification, too, cause what do they really know, anyway?----to be .11mm to .15mm, so your .006" valve is just one small toke over the line, but, due perhaps to measurement error or the "fineness" of the measurement procedure (.006 gauge fits, .005" doesn't, all we really know is that the actual clearance is somewhere between those two sizes) , etc., I would be tempted to leave it as it is, come back in a couple of thousand miles and measure again.........

 

I am so glad my shims were good except one... even aftermarket shims @ $7.50 each could really rack up price...

 

Yea, mine are set to cost me a pretty penny.

Thanks to all for your help. Once again, this is the greatest site ever. I found a chart and got the following numbers. They differ slightly from yours, Chacal. I've double checked them. Perhaps I'm looking at the wrong chart.

Front / exhaust (Range .016 - .020mm on the exhaust valves.)
1 y 270, .15mm/.006 NO fit, .13mm/.005 YES fit : GO TO ? 265
2 y 275, .15mm/.006 NO, .13mm/.005 YES : GO TO ? 270
3 y 270, . 18mm/.007 NO.15mm/.006 YES :GO TO ? 265
4 Y 275, .15mm/.006 NO, .13mm/.005 YES GO TO ? 265 (chacal says 270)

Back intake (.011 - .015mm on the intake valves)
1y270, .1mm/ .004 NO, .08mm/.003 YES : GO TO ? 265
2 y265, .0025/.06mmNO, .05mm/.002 YES : GO TO ? 250 (chacal says 255)
3 y 280, .002/.05mm NO, .04mm/.0015 YES(barely fits) : GO TO ? 265 (chacal says 270)
4 y 280 .002/.05mm NO, .04mm/.0015 YES(barely) : GO TO ? 265 (chacal says 270)

 

Math alert! Math alert!!

Or, perhaps, there is something deeper, and more sinister, at work here...... :twisted:


Let's go one step at a time:

1) Exhaust:
#4 exhaust valve
Currently installed: Y275
Measured values: .15mm/.006 NO, .13mm/.005 YES
Clearance should be: .16 - .20mm
GO TO ? 265 (chacal says 270)

- your current clearance is somewhere between .13 - .15mm.
- for gits and shiggles, let's say the clearance is .14mm (halfway in-between).
- you need to reduce the thickness ("size") of the shim in order to increase the clearance. A thinner shim will take up less space in-between the bucket and the cam lobe, therefore the clearance gets larger.
- you want to increase the clearance from the current .14mm to somewhere between .16mm to .20mm, the specified acceptable range.
- what's it going to take to do that? Well, to get from .14mm to .16mm is .02mm. That would put you on the low end of the acceptable range. To go from .14mm to .20mm, that would require an additional clearance (= a thinner shim) of .06mm.
- since shims only come in .05mm increments, then the best bet is to reduce the shim size by .05mm, which of course also increases the clearance by .05mm, too.
- thus your clearance will go from the current .14mm to .19mm, still under the .20mm limit.
- since you currently have a 2.75mm shim installed, and you want a .05mm thinner shim, the thinner size will be 2.75 - .05 = 2.70mm = a "Y270" shim.

- IF you went to a Y265 (2.65mm thick) shim from your currently installed Y275 (2.75mm) shim, you would be increasing your current clearance (.14mm) by .10mm, thus you'd go from .14mm to .24mm, which is too large a clearance (.20mm is the upper end of the .16 - .20mm acceptable range).



Work through the others until you get them right. Show all your calculations on a seperate, clean, 8-1/2 x 11" sheet of ruled notebook paper. Use a #2 pencil, and once your answers agree with mine, please stay after school and clean the erasers.....


It's much better-er if you understand the process and the calculations needed by being able to mentally "see" what is going on, and what you're trying to do, and then be able to do the simple math ("I want to increase the clearance by .05mm, my current shim is 2.75mm, so I need a .05mm thinner shim, so 2.75 - .05 = 2.70, done!"), rather than use the charts, which WILL give you the correct answers, but by gosh are they confusing to use, and things which are confusing to use lead to errors.

And you'll have to trust me on this one.......you don't want to be making errors in your valvetrain....


P.S. in case you feel like your brain is about to explode, just take a deep breath, and imagine how much better your engine is going to SCREAM once you get these adjusted correctly. Your valve clearances are way out of whack! I'll bet they had never been checked or adjusted before.......

 

OOPs Len was answering while I typed - at least we agree


For intake #4 and Exhaust #2 my cart agrees with Chacal's recommendation. Not sure why you read something different

For exhaust # 3 and 4 my chart agrees with you - 265 however look at it this way.

Measured .04 - want .11 to .15 You have a 2.80 shim. If you go to 2.70 you gaps will be .14 if you go with 2.65 you gap will be .19 which is slightly too big a gap.

Remember the chart is for 0 to .05 measured so at 0 the chart would bring you to spec. Best to really understand what is being changed. I look at the chart but then verify what I want to do as above.

Hope that helps.

 

Wiz has a right to be crabby! You have to realize he is south of the equator so while we are just moving into our riding season (through spring rains, hail, tornados, etc.) he is quickly moving into a frigid winter!

 

you all never cease to make me giggle while i'm supposed to be working. lol.

That chart that was referenced is also in the service manual.

 

I don't even want to tell you what my local shop charged for new shims but the adjustment is done.

Well, the valve adjustment certainly made the engine sound healthier but in the end I was only firing on two plugs. I found out after I put in new spark plugs and the 2nd and 3rd came out shiny clean, without a hint that they had sparked. Woops.

Now I've got another problem. After plugging in the right cylinder-shaped doohicky that the 2nd and 3rd spark plug wires go into, the battery charge is quickly drained. I have a new doohicky that I pulled off of an old bike and I intend to install it tomorrow to see if that works. Any other suggestions?

Again, forgive my newbie lingo.

 

"doohicky"

Is that a technical term?

 

WIKI Says Yes

A thing (used in a vague way to refer to something whose name one cannot recall)
What does this doohickey do?

 

Hey, Dpawl, is it dark up there?

 

Doohickie=ignition coil.

OK. So engine sounds better post valve adjustment.

However, still gutless.

It looks like she's not getting enough fuel.

I've installed an aftermarket filter and watching it, the carbs aren't getting a consistent amount of gas. Carb has been done recently, tank is clean, petcock is good, no kinks in fuel line.

In order to keep it going I need to keep switching it to PRI and back to ON to dump gas into the carb.

Any suggestions?

 

Gas cap vent hole may be clogged........when you open your cap, is there a "whoosh" sound like air is being sucked in?

Andm there is an internal tank filter (lives on top of the petcock) which may be dirty.

Or petcock may not be so good. Also, you realize that the fuel should only flow in the ON position when the engine is running.....if it flows in the ON position when the engine is off, your petcock needs rebuilding or replacing.

 

Petcock is clean and doesn't flow when engine not running in the ON position.

Actually, the gas cap is a home built job but there is a vent hole. I'll double check it. Can I test by just trying to run the bike with the cap completely off?

 

That would work. Or just loose, so that air is able to freely enter the tank...

 

Thank you. I'll try tomorrow. Also, thank you again for providing the valve shim numbers. Next time I'll buy them from you when I'm not in such a rush.

 

you may not have seen some of the humorous threads about his turn around time...... appearently when chacal fills an order he chases the post man with whips .... and that his normal procedure for standard shipping