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Discussion Starter #1
Dear Abbey,



There is a black surface coating like paint inside my TW200 2007 right side crankcase that in some places is bubbling and peeling like a paint coating attacked by solvents.

It is only on the aluminum case surface and not on any of the gears or other parts.

Can you shed some light on what this coating is and if softening bubbling has happened to anyone else and what are the ramifications, ... like clogging oil galleys?

My expectation would be to find no coating on the aluminum except whatever gum, varnish, tars are pretty normal inside any engine.

I guess if it comes down to it I will try to be happy about learning how to do a full engine teardown and clean out the loose coating, YUCK!

I'm finding almost nothing about interior crankcase coatings on numerous GOOGLE searches.



signed,

Puzzled in Cape Fear



*********************



Details:

I have just started a kick starter install on a 2007. The bike had gas in the crankcase for maybe two months while I was off on a yacht delivery ( I used to have the bad habit of leaving gas petcock on, not now! ). Thank goodness it wouldn't start when I got back and that was a big mystery so it sat for a couple more weeks. It also had a new little oil drip and it took me a long time to figure out the new little crankcase oil drip smelled of gas.



LIGHTS GO OFF, BELLS RING, BUZZER SOUNDS !!!!! carb dumped the whole fuel tank into the engine



This seemed like a good time do the kick starter install as I have been hanging on to the parts for about a year waiting to get some spare time.

Clean Oil, Fresh Gas, Spark Check and Thumper fired right up and idled for a bit to get oil circulating watching the whole time in the oil sight glass to see that the pump is picking up the oil and watch it drip back into the sump.



Pull off the right crankcase cover and start to pull the clutch and about then I notice the interior of the crankcase is painted or powercoated or something and that there are a number of places where the coating is bubbled and not well adhered . . . .. what a drag .... what about all the other places in the crankcase I can't see that must have loose coating waiting to gum and clog up the works. I am afraid a full teardown may be called for. Hard to imagine Yamaha will cover this but it seems negligent on their part to use a coating that will come off and gum up the works.
 

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It's probable that the combination of the gas and oil being left in the crank case are the culprit. No doubt the ethanol in our gas was a contributing factor.



I doubt the cases themselves have powdercoating on their interior surfaces, but Yamaha gets pretty sloppy with the side covers. If I'm right you could remove only thje side covers, fully eliminate any remaining paint from their interiors, flush the crankcase thouroughly, then refill and do a couple of oil changes back-to-back.



Definitely a new one on me. Does what you're seeing inside the cases appear to be softened powdercoating? Check your clutch before doing anything else. The binder in the clutches breaks down with prolonged gas exposure as well.
 

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The inside of the inner crank cases of my TW125 engines are painted black, but the clutch and generator covers are not, there was no evidence of this peeling when I split them for my 200cc and 225cc conversions.



The XT225 engines i have split were not painted inside.
 

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What were they thinking?



Must be a late-model thing. I've not seen it on any of my older bikes yet.
 

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Discussion Starter #6
Thanks for the feedback, I'll get some pictures posted in near future.

Also think I need to contact Yamaha to see what this stuff is .... anyone suggest a phone# for tech support in the USA ?
 

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It looks like just normal engine paint to me.



My memory was a bit fuzzy so I checked some old casing and the inside of the inner cases have heavy over spray rather than a full coat of paint.

 

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Discussion Starter #8
THAT'S IT !!!

What the heck is it doing in there?

Seems stupid, what's the point ?

A stuck carb float and soaking in gas for a while can soften it and then ??????????
 

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We used to paint the inside surfaces of cast iron automotive cylinder heads and block galleys with rustoleum to prevent sludge build-up.
 

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We used to paint the inside surfaces of cast iron automotive cylinder heads and block galleys with rustoleum to prevent sludge build-up.


A V8 could swallow an elephant through its oil passages, and if not it had an oil filter the size of yer head.



I'd love to hear what prompted Yamaha to risk this on a munchkin motor.
 

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Discussion Starter #11
I found that sitting overnight after the old gassy oil was drained allowed the soft paint to harden up. I'm going to run it and keep watch while crossing fingers !!!!

There are places where it is bubbled a bit and not well bonded and I can't get to to clean up ..... A friend suggested that alcohol was the wild card softening the coating. I don;t know.

Thanks for all the feedback, you all will hear about it if something catastrophic happens.



Meantime I will be studying the oil system flow diagrams ???
 

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I would keep an eye on the oil filter, take it out and clean periodically and also loosen the oil check bolt in the head periodically to be sure you are maintaining oil flow along the passages to the head and cam. Obviously don't go on any long rides until you are satisfied no oil ways are blocked.

When you find a clean filter I would say it's all been caught and call it good.
 

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Discussion Starter #13
uktw125,

Sounds like good advice, thanks!

I have been looking at the oil flow diagram in the service manual and while it is not as clearly done as it might be, I have a good feeling based on what I see.

Looks like the oil pump picks up from the sump thru the thimble shaped screen that is spring loaded behind the oil drain cap and then on to the filter.

If I had to be pessimistic, I now think that worst case is coating that intake filter screen with flakes of paint and starving the pump.

I will be taking your advise keep a close eye on this system.
 
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