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NeverEverJamToday

NeverEverJamToday

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the 909, California, USA
Rebuilding the cb200 rebuild. Lean out from corrosion debris that kept developing in just one sides float bowl clogged jet, burned hole. Definitely due to ethanol presence. Learning too much about that, and not enough.
Been looking into coatings so this doesn't happen again. Looking more and more like an hdpe lining (powder coat? ) might be the best option. Contacted keihin about the exact alloy these carbs were made of to try to determine options. While i received a quick response, the info available regarding materials used by keihin Japan at the time is officially "whatever was available".

So far I've tried bonderite at an attempt to alodine the bowl, unsuccessful. Tried baking vht chemical resistant enamel. Began to soften after a week submerged in fuel.
Considered por-15,but that is stated to be flexible, so not sure if it's suitable for a bowl, with all the exposed edges. 3m products i have seen specifically advise against use with gasohol. Electroplating? Brazing with silver solder?
Contacted edelbrock, their solution is fuel additives, which i'd like to avoid.

I haven't seen a solution to this besides additives on any forum. Fuel tanks yes, but not bowls.

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66Sprint said:
Problem with debris, add a fuel filter.....Problem with a corroded bowl, replace it......
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I do have fuel filters. Which was why I was perplexed when I continued to see microflakes apear in the bottom of the bowl. The corrosion was occuring in one tiny pitted section. And it wasn't apparent that the pit was due to corrosion rather than a scratch until cleaning with an ultrasonic cleaner, and the depth and color difference between the pit and surrounding surface were more obvious.
I don't see getting another bowl as the reliable solution as the same reaction will still be possible.
 
tbpmusic said:
Red-Kote
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Saw this mentioned when learned of POR-15, but it is described similiarly to the POR-15 as flexible, and I hadn't seen its for bowls specifically mentioned so considered it a potential option.


LongDistanceRider said:
CeraKote for the float bowls
Swaintech for piston ceramic coating https://swaintech.com/race-coatings/motorcycle-coatings/ $100 for a pair of pistons.
Click to expand...

Finally got to cerakote research today. Chemical resistance and durability claims are impressive for a .001' coating. Also apparently the cerakote company offers specifically a piston coat for high temp protection. If all accurate, looks promising. And I was prepared to have this done as a service rather than DIY anyway.
 
mike in idaho said:
Be cheaper to just find another carb somewhere.
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If you mean another model , maybe more modern carb with a composition not as susceptible to gasohol corrosion, yes. I concede that would be cheaper. However, if i can find a suitable coating then i solve the problem as i see it, and don't have to find a modern carb for a cb200,cb200t,ct200,cl90,qa50 ko, ct1, and rm370. The 57 metropolitan isn't a concern as that is definitely getting the new Millennium treatment. Gotta fix the bullet holes first though. #thatwillbuffrightout

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You are assuming the "corrosion" in the one bowl is due to the fuel.....IF this were true, isn't it likely that the debris flecks would have also dissolved?
Or that ALL of us would be experiencing similar problems?......I think it is far more likely you just got a bad casting, and a replacement bowl would solve your problem......But I've been wrong before.......
 
The assumption is that the ethyl in the fuel, and the moisture it absorbed, caused ongoing corrosion in the same spot which on normal visual inspection appeared to be just a scratch, but turned out to be a pit, only discovered after ultrasonic cleaning. I believe this can happen too easily again, as i did some testing with other bowls over a week using non eth fuel and denatured alcohol combos. Started to see surface deposits form in the bowl with more moisture exposure and the ethyl, but not in the non eth'd fuel.
Also, i put just straight hand sanitizer in 1 bowl with a drop off water and the same flakes started happening in a day. All cb200/t bowls


The lean out could have been a fluke, never to happen again. Ultimately i was unable to keep the bowl clean for whatever reason. But if i do just have a "bad bowl" , then i can certainly get another.
If preventing this completely is just a matter of finding the appropriate coating, rather than risking unwanted chemistry with a replacement bowl, or having to remember special additives or common avoidances, coating makes the most sense to me.

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More likely that hole in the piston is the result of detonation, caused by too much spark advance, poor gas, lugging the engine or a combination of all three. The lean-out piston failures I've seen over the years have been collapsed piston skirts. Usually happens when you are cruising along at highway speeds, one cylinder goes lean, the extra heat swells the piston until it tries to seize, damaging the skirt and smearing piston skirt material onto the cylinder wall. Once it cools off a few minutes it usually starts right up and runs,making a rattling noise in the bad cylinder(from the now excessive skirt clearance) with some oil smoke on that side.
 
mike in idaho said:
More likely that hole in the piston is the result of detonation, caused by too much spark advance
Click to expand...
Piston surfaces were visually inspected every 100 miles up until piston failure, no timing adjustments had been made since first ≈20 miles. Advancer moves freely, springs have proper tension.
mike in idaho said:
poor gas
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No fuel run in bike was purchased and stored longer than 2½ months before use. 87 with "up to %10 ethanol".
mike in idaho said:
lugging the engine
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I should hope not.

Spark plug had molten metal deposited on it, but the plug itself had not degraded.
Much of the piston material was found splashed and cooled onto the head surrounding the valves.
Burned oil can be seen in the photo above on the bottom of the piston. No such discoloration is on the bottom of the opposite/undamaged piston.
Cylinder wall, rings, skirt of failed piston have no abnormal deformation that is apparent to me.
Carb jet on side of failed piston did have debris lodged in it.
 
Molten metal deposits from localised overheating are a classic sign of detonation. Hopefully you'll figure out the cause of the problem before you run it again.
 
mike in idaho said:
Molten metal deposits from localised overheating are a classic sign of detonation.
Click to expand...
I agree. Thus my assessment.

This has been my assumption: detonation (not pre-ig) < lean condition < debris partially clogging jet < bowl corrosion < ethonol fuel+me not identifying the corrosion foothold in time. Focus points of detonation determination were the clogged jet, metal splatter, and the localized underside oil burn. In the absence of any other obvious issues.
 
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