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97 cr125 fouls plugs, jetting issue

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Hey all I have a 97 cr125 and I've been fouling plugs every tank of gas.. it is all oem except full fmf exhaust, I did put a new piston ring in it about 4 tanks of gas ago. I've been using brand new ngk Br9eg plugs.. I have tried 2 br10eg and they didn't do any better. (Yes I'm gaping them)

When I bought it the jetting was 168 main 50 slow

Then I tried 165. 50

Then I went to what fmf recommends 168  55

Then I went back to oem which is 172 main 50 slow

All of those with needle on third clip and air screw between 1.5 and 2 turns

It fouled plugs consistently (and I ride it like I stole it) but I like the way it runs with the oem jetting better, nice mid range powerband.

When I did the piston ring the power valve was full of oil.. I cleaned it up good.. 

My manual sucks, all it says about float height is 0.63 inches. And I don't know what that means..

while holding carb upside down the float looks level with the gasket surface

I mix 32 to1... at first I was using quicksilver synthetic 2 stroke oil (for mercury boat motors) but when I started fouling plugs I switched to honda premix 32 to1

I ride 1000 ft above sea level. And it's in missouri so summertime is between 50 to 100° and humid lol

I'm sure I'm forgetting something, but any help would be appreciated I'm getting tired of carrying a wrench and a spark plug with me lol

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If jetting isn't curing your rich condition, I'd check for an oil leak internally. Pull your cylinder off and look down past your crank with a flashlight to see if you have a puddle of oil down there. Could be right side crank seal or case half gasket.

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On 11/7/2017 at 10:14 PM, asian195 said:

If jetting isn't curing your rich condition, I'd check for an oil leak internally. Pull your cylinder off and look down past your crank with a flashlight to see if you have a puddle of oil down there. Could be right side crank seal or case half gasket.

I've never done that before, if I pull the entire clutch assembly out you can see it right? Any advice for getting it out?

If that's the problem I should probably go ahead and do the left side also?

And why would you think case half gasket? Just wondering

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Before tearing into anything, a crankcase leakdown test would confirm if there is a sealing issue.

A damaged left side seal is actually more dangerous as it creates an air leak, making the engine run lean.

 

If you don't remember when both crank seals were last serviced, consider them due.

Considering the age of the engine, new seals on a worn out crank (where the seal rides on) isn't much help.

 

Float / fuel height is also very important, higher than nominal richens each metering circuit.

Continue your searches to find the right specs and measuring method.

Inspect for a dirty or worn out inlet needle and seat as well.

 

Edited by mlatour

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12 hours ago, mlatour said:

Before tearing into anything, a crankcase leakdown test would confirm if there is a sealing issue.

A damaged left side seal is actually more dangerous as it creates an air leak, making the engine run lean.

 

If you don't remember when both crank seals were last serviced, consider them due.

Considering the age of the engine, new seals on a worn out crank (where the seal rides on) isn't much help.

 

Float / fuel height is also very important, higher than nominal richens each metering circuit.

Continue your searches to find the right specs and measuring method.

Inspect for a dirty or worn out inlet needle and seat as well.

 

Yeah I was looking at a thread on here about making your own leak down tester.. I will do that... eventually!

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Do you trail ride or off-road this bike rather than motocross track ride it?

 

Slower paced / non constant wide open throttle usage can benefit from leaner pilot jet and needle clip settings,

as well as a low flash point premix (not a 'racing' type).

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18 hours ago, mlatour said:

Do you trail ride or off-road this bike rather than motocross track ride it?

 

Slower paced / non constant wide open throttle usage can benefit from leaner pilot jet and needle clip settings,

as well as a low flash point premix (not a 'racing' type).

Yes I mostly trail ride, but I ride it pretty hard, any time I'm holding the clutch I make sure to keep revving it up.

I will lower the needle a notch

I've never really heard of low flash point premix. Any specific kind you'd recommend?

Thanks by the way

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Amsoil Interceptor and Lucas are often mentioned,

myself have been using Interceptor at 32:1 in my MX track ridden YZ125 since new with very good results.

 

I preventatively replace the piston & ring each season (about 25 hours) but each time they come out looking brand new, 

with about 100 hours total on the engine the cylinder's plating is now only showing a very few worn spots but is still serviceable.

Crank & rod bearings show no sign of wear.

 

Crisp jetting likely the reason but a strong point I've found for this oil is that any un-burnt excess doesn't cake up 

in the exhaust port & pipe, it remains in liquid form which can easily be cleaned off.

 

Versus constant WOT MX settings, a trail ridden 125 could easily benefit by going two steps leaner on the pilot jet

and lowering the needle.  Keeping the main jet a tad rich at premixing at 32:1 for those occasional wide open stretches.

 

I think there is actually more risk of seizure on a trail/off-road ridden 2-stroke

as straightaways (dirt roads, fields) are longer than what you'd find on the average MX track.

 

Edited by mlatour
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2 hours ago, mlatour said:

Amsoil Interceptor and Lucas are often mentioned,

myself have been using Interceptor at 32:1 in my MX track ridden YZ125 since new with very good results.

 

I preventatively replace the piston & ring each season (about 25 hours) but each time they come out looking brand new, 

with about 100 hours total on the engine the cylinder's plating is now only showing a very few worn spots but is still serviceable.

Crank & rod bearings show no sign of wear.

 

Crisp jetting likely the reason but a strong point I've found for this oil is that any un-burnt excess doesn't cake up 

in the exhaust port & pipe, it remains in liquid form which can easily be cleaned off.

 

Versus constant WOT MX settings, a trail ridden 125 could easily benefit by going two steps leaner on the pilot jet

and lowering the needle.  Keeping the main jet a tad rich at premixing at 32:1 for those occasional wide open stretches.

 

I think there is actually more risk of seizure on a trail/off-road ridden 2-stroke

as straightaways (dirt roads, fields) are longer than what you'd find on the average MX track.

 

All great advice thank you..

Manual says replace ring every 7 hours and piston every 14... not too long after I got this bike I put a new ring in it and inspected the plating, it looked great.. the bike runs like a top, until it fouls a plug haha...

I do want to go ahead and do crank seals. Supposably the guy I bought it from did have a new crank and bearings in it at some time. But I kinda doubt it

Pretty cold out now, so I've been giving my bike some tlc 

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Never use boat 2 stroke oil..............Has to high a flash point and can cause fouling issues...........

Try some Etahnol Free gasoline with the honda 2 stroke oil or Yamalube 2r and see what it does............

My bike will not even run on fuel with Ethanol in it.....................

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10 hours ago, Smokin CR 125R said:

Never use boat 2 stroke oil..............Has to high a flash point and can cause fouling issues...........

Try some Etahnol Free gasoline with the honda 2 stroke oil or Yamalube 2r and see what it does............

My bike will not even run on fuel with Ethanol in it.....................

Yes I forgot to say I only use non ethanol 91

And I did start using the honda premix.

I'll ask the guys at the motorcycle shop about low flash point oil and see what they have

Edited by lukeaulgur

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On ‎11‎/‎10‎/‎2017 at 10:02 PM, mlatour said:

Before tearing into anything, a crankcase leakdown test would confirm if there is a sealing issue.

A damaged left side seal is actually more dangerous as it creates an air leak, making the engine run lean.

 

If you don't remember when both crank seals were last serviced, consider them due.

Considering the age of the engine, new seals on a worn out crank (where the seal rides on) isn't much help.

 

Float / fuel height is also very important, higher than nominal richens each metering circuit.

Continue your searches to find the right specs and measuring method.

Inspect for a dirty or worn out inlet needle and seat as well.

 

Just an FYI but a leak down test on a 97 cr125 will be useless.  That motor holds no pressure, it all blows right past the powervalve.  I tried to leak test my 94 and when it wouldn't hold pressure, I called Eric Gorr and asked him about it and he said it was normal.  You are going to have to do normal maintenance on it to find the problem, I would start by replacing both crank seals since you can do that without taking the top end apart. Also, the BR10 is a colder plug than the BR9 which would make it foul easier.  If you want to try a different plug than the br9, I would try a BR8 but if the bike is mechanically sound and jetted correctly, it doesn't need the hotter plug. 

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Well thanks everyone for the advice, I've got her all torn apart right now 20171127_175713.thumb.jpg.76833346dcf9aafcd94e8d84ecdd2e2d.jpg

Just did right side crank seal, water pump seals, kick start seal, and the power valve seal which I'm pretty sure was my problem, the power valve linkage was full of transmission oil, and the power valves were also covered. The bottom of the crankcase didn't have any oil at all, but I'm doing all of the seals anyways...

Got a new honda piston holes drilled on exhaust side 20171127_175008.thumb.jpg.7e916dca353b39458675b72a4a8f8808.jpg

I ordered an eBay clutch kit. It was cheap, might as well try it!

But I do appreciate everybody's advice I'll keep you updated

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My advise:

next time invest in a better piston!

Stock Honda pistons are cheap quality and shrink A LOT as soon as the engine gets hot. That's what makes this rattling noise once you have just a couple of hours...it's the cheap piston moving in there because of excessive play. AND you can get just two sizes which leaves a lot to be desired...you need a good piston which holds its size at a thight play.

So i'd highly recommend you get your bore measured and get a quality piston from Vertex/Wössner...at 0,05mm / 0,002" play. They come in up to 5-6 different sizes from 53,93-53,97mm

 

AND i can highly recommend to follow my setup Tips&Tricks for the HPP valves when assembling everything:

 

 

Edited by nino
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7 hours ago, nino said:

My advise:

next time invest in a better piston!

Stock Honda pistons are cheap quality and shrink A LOT as soon as the engine gets hot. That's what makes this rattling noise once you have just a couple of hours...it's the cheap piston moving in there because of excessive play. AND you can get just two sizes which leaves a lot to be desired...you need a good piston which holds its size at a thight play.

So i'd highly recommend you get your bore measured and get a quality piston from Vertex/Wössner...at 0,05mm / 0,002" play. They come in up to 5-6 different sizes from 53,93-53,97mm

 

AND i can highly recommend to follow my setup Tips&Tricks for the HPP valves when assembling everything:

 

 

Great thread, thanks. I can't find any 98 power valves on eBay at the moment. Thanks for part numbers tho!

And about the piston, my local machine shop is closing! So they aren't taking any more orders. I dont know of any others in my area. But he had that honda piston in stock, pre drilled and sanded for $50 so I just got it.. but they usually use wiseco piston, I take them the cylinder and they order the exact fit piston and ring ( so they say ).

Anyways, how do you feel about wiseco piston? Right now my son has a 3 wheeler and a 4 wheeler and I have a bike with wiseco piston all ordered by the machine shop, and they seem to hold up good to me. But I was just asking your opinion because you clearly know your stuff about these 125s'!!

I will look up the piston you mentioned above and check that out.

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I see that "sanded" piston. Hmm - why would you do that other than to hide a USED piston??

Anyway - i personally don't like Wiseco. The only failure i ever had in 30 years was with a Wiseco. I personally would suggest Vertex or Wössner. And most important is to actually know your bore (have it measured!) so you can order the correct piston size which is neither A or B ;)

 

That clutch lever can be pulled out but you need to remove the flywheel first. But that lever itself has no retention.It just comes out. By the way - that's one part which is often overlooked on those older CR engines. Its edges get rounded from use an will make for sluggish clutch action. This lever costs about 30$ and is definitely on the list of parts that need to be replaced after a couple of years!

Here's such a used lever:

37843474985_733041b949_z.jpg

And here's the worn edge/tip of that lever. That long rod which goes through from the left side to the clutch hub rides on that edge. If that edge gets worn the clutch action isn't the same anymore.

23866065607_8dbeb1dc61_z.jpg

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