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Discussion Starter #1 (Edited)
I have a 2019 Grom with a Takegawa 143 BBK and cam, SUP oil pump, Kitaco clutch cover, Yosh complete exhaust, Dingerbuilt short intake, and a PCV with WBC2 installed. Whilst driving down the road at WFO throttle and redline, the motor start making a knocking noise then quit moments later. The piston is roasted and the cylinder walls are torched. I have installed a new 181BBK with oil cooler. While the engine was apart, I inspected all the accessible oil ports, oil pump, filter and found a bit of what appears to be grey gasket material in the filter and screen. I was wondering if there is a blocked oil line. Is there an oil jet that sprays the bottom of the piston or is the piston oiled solely by the splashing action of the rotating crank? Does anyone have any ideas? See attached pics.

Thanks,

UH60Hwkdrvr
 

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I found what looked like a small piece of gray rtv on my oil strainer during my first oil change. Is this the first time you have pulled the strainer?
 

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Looks like your problem might be not enough piston gap on the top ring and the second ring. I always error on the larger size for my piston ring gap.

Your oil screen should be checked about 50-100 miles into the break in to remove any crap that clung on to your engine case such as dust in the shop, pet hairs from dogs or cats and such. I always drop my engine oil at 50 miles break in just to check my oil screen and since I have a Kitaco clutch side cover I don't worry about to much crap but it does happen if you are not careful about pet hairs or dusty shop.

When I use any grey sealant on my crank case when putting my build back together I only put sealant on the outer liner of the case and near the oil screen.

Take your engine a part and remove the crank/rod and also remove the transmission bearings to check from wear from any metal particles that might have gotten into the racers. Spin the bearings in your hand and feel if you have resistance due to bearings being contaminated with metal crap, the bearings should spin EZ with no resistance, also check the crank bearings and rod bearings for the same results.

Look at the piston pin to rod connection to see if is not worn and if so replace them.

You should have a A/F monitoring gauge on your exhaust pipe to check that your A/F ratio is correct for all RPM range and at the higher RPM range your A/F should be in the 12.6-12.9 to keep the engine cool .

I monitor my groms by having a duel gauge setup to check my head temps and cylinder temps and just by looking at those readings plus my oil temp readings I can predict if the engine is running ok at various temps. My cylinder and head goes between 220F-260F depending if I'm moving or stopped at a stop light and my oil temps go between 169-229F depending on the riding condition or if it is summer time or winter time riding.

on my yell/wht grom you can see a red unit on my left side handle bar which is a thermometer duel channel setup and the pick up wires are attached to my head and cylinder for monitoring the temps. It's a EZ cheap setup and I bought the unit from ebay around $20+ with free shipping, that way monitoring my temps is a breeze.
IMG_5353 copy.jpg
 

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Discussion Starter #5
Why is the piston gouged on the side?

What was your temperature and air/fuel ratio when it popped?
Somewhere between "core of the earth" and "surface of the sun" hot. I don't really know as I don't have a temp gauge installed.

UH60Hwkdrvr
 

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To me it looks like a temp problem... I've got an almost identical setup and even with a small oil cooler it still gets close to dangerous levels of heat.

260F oil temp is not out of the ordinary but on the dangerous side and I see it regularly when going up a hill in hot weather.
 

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Discussion Starter #8
I am thinking a Lack-O-Oil to the piston may be the problem. I am installing new parts, properly gapped rings, and an oil cooler. We will see what happens.

UH60Hwkdrdvr
 

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To me it looks like a temp problem... I've got an almost identical setup and even with a small oil cooler it still gets close to dangerous levels of heat.

260F oil temp is not out of the ordinary but on the dangerous side and I see it regularly when going up a hill in hot weather.
Fix your up heat problem by installing those modified oil pump with the extended copper tube, it works to help suck the oil when the grom is pointing up hill, since the oil goes towards the back side of the crank case.
 

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Fix your up heat problem by installing those modified oil pump with the extended copper tube, it works to help suck the oil when the grom is pointing up hill, since the oil goes towards the back side of the crank case.
I have a high flow pump. I don't think the incline is that extreme that I need the copper tube pickup for better circulation. I think it has more to do with the load on the motor and pushing my fat ass up Hwy 17.
 

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I have a high flow pump. I don't think the incline is that extreme that I need the copper tube pickup for better circulation. I think it has more to do with the load on the motor and pushing my fat ass up Hwy 17.
Correct. You won't need a pickup tube on the oil pump during normal riding conditions. That's more for guys that wheelie blocks at a time.

It's hard trouble shooting without having any data to look at.

How old was the 143cc kit when it blew up?
 

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I have a high flow pump. I don't think the incline is that extreme that I need the copper tube pickup for better circulation. I think it has more to do with the load on the motor and pushing my fat ass up Hwy 17.
from most my riding buddies in San Jose we notice the extra tube does help reduce temp going up hill and we are running 170-4v, 181-4v and larger BBK kit engine going full throttle, high flow pump don't mean nothing if you can't pick up your oil at a angle going up hill. If you have a Kitaco clutch side cover with the glass oil inspection, raise your front wheel up and look into the glass you will not see any oil or a little oil, there is limit way the pump can pick up a good gulp of oil to cool down the engine the extended copper tube does that.

Ride safe but fast and ride it like you stole the grom
 

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from most my riding buddies in San Jose we notice the extra tube does help reduce temp going up hill and we are running 170-4v, 181-4v and larger BBK kit engine going full throttle, high flow pump don't mean nothing if you can't pick up your oil at a angle going up hill. If you have a Kitaco clutch side cover with the glass oil inspection, raise your front wheel up and look into the glass you will not see any oil or a little oil, there is limit way the pump can pick up a good gulp of oil to cool down the engine the extended copper tube does that.

Ride safe but fast and ride it like you stole the grom

With a stock pump and stock amount of oil, you are looking at a front wheel raised about 3 ft off the ground before it starts sucking air.... this isnt the OP's problem.


To the OP, there is an under piston oil squirter but the oil screen would stop anything that would clog it or any of the other oil orifices for that matter. Looks like things were tight, and got too hot. Do you have an oil cooler on this setup?
 

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Discussion Starter #14
The kit was about 1300 miles old when it let go. I have a Kitaco oil cooler for the new setup. I should have it up and running in a few days. Hopefully I have solved the blown motor issue.

UH60Hwkdrvr
 

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It's gotta be the lack of oil cooler.

When I installed my 143, I ran it without a cooler, and it started overheating after about 15 minutes of riding. Didn't ride any more until I got the cooler installed.

I can see how 1000 miles would destroy the piston if you kept running it that way.
 

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Discussion Starter #16
New Takegawa 181 BBK installed with a 16t front and 32T rear sprocket. The 181 motor is strong and the new gearing makes the bike faster. This is probably how Honda should have built the bike....it was too anemic with the 125 displacement. I Added an oil cooler to keep the temps low. We shall see how this works out.

UH60Hwkdrvr
 

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You need a way to monitor your cylinder head temp. I suggest the Trail Tech TTO CHT gauge which reads from the base of the spark plug. If you keep this temp under 375F, you'll be good. You can run the largest oil cooler possible, but it won't keep your piston from overheating because these engines are not oil cooled - they are air-cooled. The best way to keep the cylinder head temp cool is by make sure ring gap is correct, and Air fuel ratio is on the richer side.
 

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Discussion Starter #18
I am happy to report that the new motor seems to be running strong. I have about 100 or so miles and everything appears to be fine...no leaks, no unusual noises, etc.... I think the 181 is the way to go. However, I did swap out the 16/32 gearing for a 16/34 setup. I may even try the 15/32 gearing to see if that feels better.

UH60Hwkdrvr
 
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