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Discussion Starter #1 (Edited)
I pulled the spark plug from a '88 TRX350D today and to my surprise it had an NGK D6EA plug in it, which isn't one of the ones listed in the service manual for the bike. It is carboned up pretty good. Which plug do you guys recommend for it? I see there are 3 NGKs (DR8ES-L, DR8ES, & DR7ES) listed as compatible in the manual. I'm thinking the fouling might get worse if I use the colder plugs.

I have a compression gauge, so I may as well check it before I put the new plug in. Any special procedures for doing that on these bikes, like hold the throttle down or etc?
 

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The spark plugs i cant really make a recomendation on since im not into utility quads. But the compression test i can help with.
1. Make sure the battery is charged 100%(i usually put my battery tender on it)
2. Turn kill switch on handlebar to off position
3. Hold throttle wide open.
4. Crank it over until the needle stops climbing. (Generally 5 to 10 turns).
 

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Discussion Starter #4
The spark plugs i cant really make a recomendation on since im not into utility quads. But the compression test i can help with.
1. Make sure the battery is charged 100%(i usually put my battery tender on it)
2. Turn kill switch on handlebar to off position
3. Hold throttle wide open.
4. Crank it over until the needle stops climbing. (Generally 5 to 10 turns).
10-4, thanks! About the same as any other engine looks like.

I went ahead and put the DR7ES it for now. It runs fine but I will pull & check it after running it some.

I've got to check the exhaust for leaks too. Every time I ride it much at all I smell like exhaust when I get off. I've got a homemade smoke machine I made a few years ago that should be just the ticket for checking it.
 

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Discussion Starter #5
Compression is 150psi, which is a little low according to the manual spec. Not sure if that’s typical with a machine this age or not. I do not hear the valves ticking but I have not checked them yet. The new spark plug was already carboned up since putting it in yesterday afternoon and it wasnt riden much. Not wet with oil or anything, just a dry carbon deposit.

Smoke tested the exhaust and didn’t find a leak except at the spark arrestor clean out plate.
 

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Discussion Starter #6
I just came across a post by retro that says using an adapter on the compression tester can cause a low reading since it adds volume. I had to use the adapter with my OTC tester, so maybe that's the issue or at least part of it. I could wet test it. I don't have a leak down tester or I'd check that also.
 

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Your 1st plug pic looked like it had been running rich with a bit of oiling. So the carb/air cleaner needs some work and its probably got four leaky valve seals, minimum. It may be getting weak in the compression department too.

Someone probably put the hotter range plug in it in an attempt to sweep those problems under the rug, but higher heat range plug don't ever hide or help problems, plug just runs a bit hotter. LOL
 

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On an old machine like this the needle can wear the taper to a smaller diameter which will cause a slight rich condition. You can replace it and it's holder/jet or lower the needle position with the clip. Leaning the fuel screw may help as well. As previously mentioned it looks like a rich condition and a little bit of oil too. A carb overhaul and new rings may be all that's needed if you catch it in time. Running with worn rings just wears the piston and cylinder at exponential rates.
 

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Yep, these small displacement ATV motors are very unforgiving to swept volume losses in compression tester adapters. If yours does not have a low-pressure schrader valve in the adapter the readings you'll get with that adapter are useless. The rubber o-ring rarely provides a good seal on the head either, most times they leak pretty bad. So your 150 PSI reading might be 20-50 PSI lower through that adapter, depending on its volume. If at all possible I generally leave the o-ring off and use a common spark plug gasket on the fitting and snug them down tight.

EDIT: Another problem with adapters is most of them are short... where you have a long reach spark plug hole they rarely fill half of that hole.
@misterclean59 clearly understands motors inside an' out. Excellent post an' brain candy... :)
 

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Discussion Starter #10 (Edited)
Your 1st plug pic looked like it had been running rich with a bit of oiling. So the carb/air cleaner needs some work and its probably got four leaky valve seals, minimum. It may be getting weak in the compression department too.

Someone probably put the hotter range plug in it in an attempt to sweep those problems under the rug, but higher heat range plug don't ever hide or help problems, plug just runs a bit hotter. LOL
I’m sure my dad can put whatever plug the Honda shop sold him in it. He bought a new bike 6 or 8 years ago and pretty much parked this one except for some grunt work around his place now and then.

He’s anal about not using ethanol gas and always treats his gas, but I doubt seriously the carb has ever been off of it, so it could probably use a cleaning/rebuild. I cleaned the air filter a few weeks ago.

It doesn’t use any oil and the plug was not wet, albeit black with soot/carbon. It was also only finger tight. I’ve got a scope and meant to have a look in the chamber but forgot. I’ll probably wet check the compression though, so I’ll have a look around in there then. I’ve been meaning to get a leak down tester to check my old pickup, so I may do that also.

The adapter on my compression tester does not have a valve. The end up the hose that screws into it does. The adapter is also a lot shorter than the plug. I’ll look around and see if I have another one. Use too but haven’t seen it around in a while, so it may have walked off.
 

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It sounds like you are fine with compression since it doesn't use a bit of oil. I wouldn't put any money into more tools to get better accuracy, just adjust the valves and check the timing chain by yanking the slack adjuster and see how much plunger length remains.

As @misterclean59 mentioned, you'll probably find a worn jet needle and holder/needle jet in the carb making it run rich above idle speed. A Shindy kit will have everything you'll need... can't remember if you get a new needle and holder in those kits though...
 

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Discussion Starter #12
retro said:
It sounds like you are fine with compression since it doesn't use a bit of oil. I wouldn't put any money into more tools to get better accuracy, just adjust the valves and check the timing chain by yanking the slack adjuster and see how much plunger length remains.
As @misterclean59 mentioned, you'll probably find a worn jet needle and holder/needle jet in the carb making it run rich above idle speed. A Shindy kit will have everything you'll need... can't remember if you get a new needle and holder in those kits though...
Can you simply take the 2 bolts out of the adjuster, remove it, and put it back? Or do you need adjust it?

I’ll check out the shindy kits. The carb parts are kind of pricy piece by piece from Honda.
 

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Take the small plug bolt out of the end of the adjuster 1st. 8mm socket gets it I think? Then roll the motor over by hand in its normal direction of rotation until it is on the compression stroke. All four valves will be closed and there will be no load on the camshaft at this point. Do NOT turn the motor over backwards at any time, not ever.

Then take the two bolts out of the adjuster and remove it from the cylinder. The adjuster will auto-extend to its maximum length under its own spring pressure as you pull it away from the cylinder. Once it is out simply hold it back against the chain guide firmly with your fingers, as if you were gonna reinstall it.

Now make a note of the distance between the adjuster gasket and cylinder. Any gap 3/8" or narrower indicates that the chain is completely worn out and should be replaced immediately. Between 3/8" and 7/16" means ya got a bit of time to make plans and order in all of the parts. 1/2" or more gap means the chain and guides are still in good condition.

To reassemble it, use a narrow flat blade screwdriver (inserted in the hole in the end where you removed the small plug) to crank the tensioner back in to its shortest length, then stick a piece of mechanics wire in alongside that screw to jam it temporarily to hold the tension back while you reinstall the two mounting bolts. The service manual shows ya how to use that trick... Once you've got the two bolts snugged up insert your screwdriver again and release the wire that you jammed in there. The tensioner should auto-extend back out against the chain guide rapidly, you'll hear it.

Final two steps, rotate the crank again by hand in the normal direction for at least two complete turns. Then put the plug back into the end of the tensioner and snug it up.

Done. :)
 

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Discussion Starter #14
Take the small plug bolt out of the end of the adjuster 1st. 8mm socket gets it I think? Then roll the motor over by hand in its normal direction of rotation until it is on the compression stroke. All four valves will be closed and there will be no load on the camshaft at this point. Do NOT turn the motor over backwards at any time, not ever.

Then take the two bolts out of the adjuster and remove it from the cylinder. The adjuster will auto-extend to its maximum length under its own spring pressure as you pull it away from the cylinder. Once it is out simply hold it back against the chain guide firmly with your fingers, as if you were gonna reinstall it.

Now make a note of the distance between the adjuster gasket and cylinder. Any gap 3/8" or narrower indicates that the chain is completely worn out and should be replaced immediately. Between 3/8" and 7/16" means ya got a bit of time to make plans and order in all of the parts. 1/2" or more gap means the chain and guides are still in good condition.

To reassemble it, use a narrow flat blade screwdriver (inserted in the hole in the end where you removed the small plug) to crank the tensioner back in to its shortest length, then stick a piece of mechanics wire in alongside that screw to jam it temporarily to hold the tension back while you reinstall the two mounting bolts. The service manual shows ya how to use that trick... Once you've got the two bolts snugged up insert your screwdriver again and release the wire that you jammed in there. The tensioner should auto-extend back out against the chain guide rapidly, you'll hear it.

Final two steps, rotate the crank again by hand in the normal direction for at least two complete turns. Then put the plug back into the end of the tensioner and snug it up.

Done. :)
Thank you for the details, retro. I appreciate it. I'll check it out as soon as I get a chance.
 

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non-ethanol gas

your dad is correct about not using ethanol gas. using ethanol gas, despite the warnings, :smile
i dont have a definition for that.
 

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Discussion Starter #16
your dad is correct about not using ethanol gas. using ethanol gas, despite the warnings, :smile
i dont have a definition for that.
Yeah, he won't put it in anything except his daily driver autos. For everything else he uses treated non-ethanol. I try to be the same way, but I'll run ethanol sometimes when I'm in a pinch and intend to use it up pretty quickly.
 

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ethanol-gas.

its more important, to have non-ethanol, when using atv's, weed whackers, an chainsaws.
newer car's are designed to run on the junk. putting real gas in a newer car, or, what ever, can cause damage.
 
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