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93 XR600R with a problem

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Mod: I've re-posted this same post to the garage / bike specific forum in hopes of more traffic, sorry for the duplication.

 

Hey folks, new to the forum, hopefully I'm not being redundant here but I've got a problem with a 93 XR600R where it's starting to drive me a little batshit.   :)

 

I bought used a few years ago, have been tinkering with it getting it ready to (likely jump on the group buy here) install a dual sport kit and get some riding in.  The issue is this.

 

Acceleration off the line goes something like...  Gang busters up to about 2K RPM then falls on it's face, sputters, pops, shoots flames out the exhaust, then gets up and goes, albeit roughly, the power pours on...

 

It's a bit of a bitch to start, you have to get it just right on the compression stroke, have the throttle a 1/4 turn and a good bit of luck.

 

Brand new (tested) XR's Only Mikuni 41mm flat slide, jetted and needle set for my altitude, carburetion shouldn't be the issue.  I suspected an issue with the carb, to the point where I sent it back to Mike (the carb guy at XR's Only) and he went through it, confirmed the build and installed it on an XR600 this past weekend and said it performed perfectly.  The carb it on it's way home now so I'm still very likely going to have this problem.  Mike suggested the jumped tooth possibility on the cam / chain.  So just this-evening I've adjusted the valves and the one intake was only a tad loose.  Having the crank at TDC on the compression stroke, everything looked as it should, I was hoping it was the jumped tooth, that would account for how it runs and starts but this proved to be a dead end.

 

Other do-dads, it's got an FMF silencer and header.

 

I believe a head job by XR's only a long time ago.

 

The decompression has been disconnected from the kicker.

 

Was raced in California (Baja) so it's likely had other work done, it's clean, powder coated, tight, engine internals look meticulous / clean.

 

Over-all the bike was well maintained, well cared for, just need to get past this issue where it's hard starting and falls on it's face off the line and I'll execute my plan to get it dual sporterized.

 

Time has passed, I've since tried a myriad of jetting combinations to no avail.  The bike does seem to run better (sometimes) if I just leave the choke on...  However, regardless of what jets etc, the plug is always really black...

 

Just last evening I checked for compression at TDC.  I managed to get TCD, even though the auto-decompression makes that a bit of hell (how is one to account or that not being a cause of issues?).  I was able to remove all the rocker covers, get TCD and then forced air into the spark plug hole with a compression tester and it held perfectly.

 

What I'm wondering at this point, is if the valve timing is off a tooth, there doesn't appear to be a way to check this without pulling the valve cover. This leads me to new questions to all your Thumper Heads out there. 1) Can you pull the valve cover without taking the engine out of the frame? 2) If it's a tooth off, wouldn't all the valves be closed at TDC? 3) Would it be wise to disable the auto-decompression and how is that accomplished?

 

I'm at my wits end, this bike is cherry but for the "running like crap" part, it's like having a hot fudge sundae in front of you that you can't eat... With a cherry on top.

 

Lastly, what else has been checked out...  I've taken an ohm meter to all the electrics that could be suspect, the coil didn't seem to be quite right so it's been replaced, along with a new cap and plug.  The stator checks out, the CDI, not really sure how to check, the crank sensor also checks out.

 

Final final thoughts... I don't know what all has been done to the engine, it was raced, it could very likely have an "upgraded" cam, oversized piston, higher compression, i really just don't know.  What I do know is I think the work was done by XR's Only, i'm going to call them later today to see if they have any records on this specific bike.  (I know I'm likely dreaming they'd keep a history)  Again, help, HELP!  I'm losing my mind!

 

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I should add, in general, it misses, pops, sputters and doesn't like to run above idle, but under load it becomes very apparent there is a problem.  it's like the timing isn't advancing or something, I'm still suspecting the crank sensor or maybe the CDI.  Mechanically seems like everything is spot on, but for the frustration of not being able to confirm the cam timing without removing the valve cover (ripping the engine out)...

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I am having the exact same issue by the sounds of it. You may have a tooth off on the cam however I did not when I checked. It is possible to take the valve cover off inside the bike you need to remove the carb and various other stuff attached to the valve cover and wiggle it out carefully. First time I did it thought it would never come out but after doing it multiple times trying to find the issue its gotten easier. Putting it back on is even harder but it can be done. Anyways from the research I've been reading since I haven't really gotten an answer from my post is that if it were the cdi unit the bike wouldn't run at all. I was reading something last night that said timing chain could be to far stretched out as well as the auto decompress is bad because you changed change all of that at the same time. Hopefully this helps if you happen to figure it out to be something else let me know because I'm scratching my head as well on this issue

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ImageUploadedByThumper Talk1408473341.878019.jpg

First off, you said the valves were adjusted and only one was a little loose. They are supposed to have play in them as per manual. As the engine reaches operating temp, the valves expand narrowing the gap. If you haven't already, get a manual you can find a downloadable one fast and cheap. Second, I still think it's carb related. Have you tried messing with the jets at all? I have attached a pic from a crf150r manual but the principles are the same.

Edited by thumpthis723

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<<shoots flames out the exhaust>>
Incomplete combustion causes fuel build-up.
Need to look at the spark on an analyzer... but
it could be anything causing this..
Check plug color. spark gap etc
Try turning off fuel tap and see how she goes..should run lean as fuel runs out.
otherwise it could be flooding.

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Thank you all for the suggestions and information so far, I'll address the questions raised below:

 

It's good to know the valve cover can come off without yanking the engine, thanks Oddengineer!

 

Valve adjustment, I checked the manual and set them to specification (if I recall, it's .005 exhaust .004 intake) whatever it was, I looked at the book 5 times while I was setting them, so I don't think that's it.

 

I've tried multiple combinations of jets and needle positions, from lean to rich, nothing there seems to make much of a difference, aside from that, I sent the carb back to XR's Only and Mike went through it, checked it for the proper internals and then put it on an XR600 at the shop and he said it was perfect.  I think we can rule out fuel..

 

Spark is nice and blue with a good strong kick, brand new plug (addresses gap), brand new coil and spark plug cap (the old cap didn't read ANYTHING on the ohm meter!).  None of this seemed to make a difference though.  The plug is always black, and if you don't give it a strong kick, the spark is lame and orange.  My buddy and I put a timing light on the bike and the strobe looked really odd, like it was missing and out of sync, both the lame spark and weird timing thing both make me lean toward ignition and subsequently the CDI.  (Ricky Racer, yup, ignition)

 

I ordered a CDI from Rick's Electrics, we'll see if that does anything, it's worth the $45. dollar gamble, if it doesn't pan out I'll have a spare.

 

As far as ignition, that's the only black hole, everything else you can test with an ohm meter and it's got a new coil (the old coil didn't ohm out just as it should).

 

Valve timing, i'm leaning toward this as the fall back, if the CDI doesn't fix it, I'm going to yank the valve cover and check out the cam / gear position and see how it looks, I'm liking the suggestion that perhaps it's a stretched chain.

 

Thanks for the input gents, I've been working on this for a long time, intermittently as I burn out after a bit and then come back to it but I'm determined to get this thing squared away, so every little bit helps.  I think we're close with narrowing it down this week with ruling out mechanical, it's got killer compression, no valve leak down.  The only things at this point are the timing chain question and the funky ignition.  If the CDI box doesn't pan out, that's it, I'm going to get into the valve cover. 

 

I curse Honda for not putting inspection covers so you can see the cam gear and timing marks!  *shakes fist

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It is not unknown for cold solder joints in the CDI to break.  That can cause intermittent connections internally, not necessarily outright failure.

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PerryMachine: West of Philly, near Pottstown.

 

DaveK18: OEM carb behaved the same way, which what had originally lead me to believe it was carb issues, i fidded with that OEM carb for a while, cleaning, rejetting and it wouldn't change a thing, so I put the Mikuni flat slide on there, of course, yep, issue is still with me....

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Not to insult, but have you checked the air filter to make sure a rag didn't get sucked in there, or a mouse nest happened?  I had a Nissan pickup once that sucked the oil checking rag into the intake and blocked it off.

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Acceleration off the line goes something like...  Gang busters up to about 2K RPM then falls on it's face, sputters, pops, shoots flames out the exhaust, then gets up and goes, albeit roughly, the power pours on...

 

It's a bit of a bitch to start, you have to get it just right on the compression stroke, have the throttle a 1/4 turn and a good bit of luck.

 

 

The decompression has been disconnected from the kicker.

 

What I'm wondering at this point, is if the valve timing is off a tooth, there doesn't appear to be a way to check this without pulling the valve cover. This leads me to new questions to all your Thumper Heads out there. 1) Can you pull the valve cover without taking the engine out of the frame? 2) If it's a tooth off, wouldn't all the valves be closed at TDC? 3) Would it be wise to disable the auto-decompression and how is that accomplished?

 

Lastly, what else has been checked out...  I've taken an ohm meter to all the electrics that could be suspect, the coil didn't seem to be quite right so it's been replaced, along with a new cap and plug.  The stator checks out, the CDI, not really sure how to check, the crank sensor also checks out.

 

Final final thoughts... I don't know what all has been done to the engine, it was raced, it could very likely have an "upgraded" cam, oversized piston, higher compression, i really just don't know.  What I do know is I think the work was done by XR's Only, i'm going to call them later today to see if they have any records on this specific bike.  (I know I'm likely dreaming they'd keep a history)  Again, help, HELP!  I'm losing my mind!

 

A 93 should of had the cam actuated decomp and no kicker decomp.  If it has an upgraded cam the auto decomp is most likely removed. I just replaced a CDI on a 97 600 that the owner swore was a bad stator. His complaints were primarily coughing and stalling after continuous rides of 30 minutes or more( heat saturation of electrical components). You will always get the answer "stator" first on TT. Again my personal experience has been the cdi box first with stator being about 1/3 as likely but that's just me. After putting the used 85 CDI on he has no further problems. There are resistance tests that can ascertain if a CDI is bad but passing those values does not guarantee said box is good. If there is an intermittent short inside the resistance tests do not necessarily detect that. Substitution is the only way to verify the condition of the CDI.

Edited by valvesrule

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Substitution is the only way to verify the condition of the CDI.

This is true generally..  buzzing out components is only a rough test to check continuity.

Resistance tests are of value only if you know what you are doing.

Edited by rogervize

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I prefer to test the stator, or anything else for that matter under load and running.  Your ignition lead out of the stator should be 70 volts a/c at least when running.

 

check voltage drop on your grounds too.  Especially CDI ground.

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I prefer to test the stator, or anything else for that matter under load and running.  Your ignition lead out of the stator should be 70 volts a/c at least when running.

 

check voltage drop on your grounds too.  Especially CDI ground.

 

Davek18:  So I got around to checking the stator while running just a bit ago.  I have three wires coming from the stator, and I suspect it's aftermarket, the jacket on the wire/bundle coming out of the case is Red.  The three wires are 1=black w/red stripe, 1=green and = white.  The white and green wires make 3 to 5v A/C while running, the Black w/red stripe wire 40-50v depending on the RPM.

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All of those voltages are too low from my experiences.  The wires coming out of the stator will either be lighting or ignition, excepting of course ground (if it has one) and neutral light.  The lighting wires need to feed 12 volt bulbs so they need to be 12-14 volts at least i would think.  I know the ignition lead on my XL puts out 50 just kicking and 70 and more running.  I am sorry I have forgotten the higher voltage it achieved but in any case I would say yours is  way too low. 

 

Is there a ground wire into the stator that hooks to the frame like a Ricky?  My gut feeling is the stator internal ground is compromised.  If one of the lighting  coils shorted they usually take out themselves and possibly another sharing the same ground, but ignition should be ok.   Test the stator for ground with a meter, and better yet if possible under load with a voltage drop test.  Have tested the chassis ground? 

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All of those voltages are too low from my experiences.  The wires coming out of the stator will either be lighting or ignition, excepting of course ground (if it has one) and neutral light.  The lighting wires need to feed 12 volt bulbs so they need to be 12-14 volts at least i would think.  I know the ignition lead on my XL puts out 50 just kicking and 70 and more running.  I am sorry I have forgotten the higher voltage it achieved but in any case I would say yours is  way too low. 

 

Is there a ground wire into the stator that hooks to the frame like a Ricky?  My gut feeling is the stator internal ground is compromised.  If one of the lighting  coils shorted they usually take out themselves and possibly another sharing the same ground, but ignition should be ok.   Test the stator for ground with a meter, and better yet if possible under load with a voltage drop test.  Have tested the chassis ground? 

Thanks for the info, I'm not sure where the grounds are on this bike, what are the typical locations for a 93?  Yeah, the three wires coming out of the stator are it, they join wires in kind under the seat and snake back into the harness.

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I don't know where they put the grounds on an XR.  I am more familiar with the XL.  On the XL one goes to the battery, and another is mounted to the frame near the coil.  Traditionally on Honda all grounds are green wires.  I am not opposed  to adding an additional wire to the frame from the harness or select components.

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Hello All,

 

Just to circle back and close out, it turned out to be the stator. I installed a 200w Ricky Stator and it made all the difference. I was able to test the old stator on the floor of the garage and I got OL (open loop) on both the green and white wires, 8 ohm on the black/red. What's amazing is that it ran at all.

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