New Motor Destroyed

[bluck]

Hey guys I bought a new motor from bekits.com (second motor from them). I got it started up first time yesterday night and drove it about 3-4 minutes no problem (speed carb). Today I received an RT Carb from Dax. As I was putting in the new throttle cable I noticed that there was a small metal flake inside. No problem I take it out I give it a quick check for more flakes just find one more outside the carb. Then I put it in the motor and then tighten everything. I don't run it till about 3 hours later(took a nap). I go ride it and turns on runs nice and smooth 20 seconds later loud pop. It suddenly stops the bike from moving (I was going 13 mph GPS on my phone, always have it on when I ride). I pull in the clutch quick and prevent a possible fall. I then decide to turn it on again and it struggles to turn and doesn't idle if I pull in the clutch. I wait 2 minutes and try to turn it on again and works good a little weaker than before and it's riding as long as I'm giving it throttle. About 2 minutes later longer than before it pops not as loud and I pull the clutch in save myself I was going 16mph. I get home open the engine up and see the following (pictures):

Question is what could have caused it was it the new RT carb with its flaking metal or what? When I opened it up one of the piston rings was broken in half. So frustrating since I waited a whole month and I bought a full kit just for the motor since he didn't have single motors for sale and he isn't selling PK80 motor parts alone for now. He as in (bekits). So what could have happened? I suspect the RT carb.

 

[Kioshk]

Well, you're definitely in the market for a new top-end (like $35). It looks like a classic case of something very hard being pulled up through the transfer-port and getting wedged between the piston and cylinder-wall during the down-stroke. Clean out the case and see what's in there. It's also possible something got in there during the carb install, Check to see if the piston's lower ring's index-pin is still there; that little piece of steel is a likely culprit if it got loose. Since your combustion-chamber seems unscathed and if you're desperate, you could probably still run that top-end if the top-ring is still viable. Just clean up the piston damage, and remove the cracked transfer-port wall. Grind off any protuberances. You have my sympathy for a bad initial experience; these engines can be a crap-shoot, but when you've got a good one running well, it's all worth it. Going forward, I highly recommend disassembling and reassembling these engines yourself when you get them new. This way you can make sure everything's clean and properly assembled.

 

[crassius]

yeah, could have just been a piece of something in motor, or something came in from carb - my guess would be from motor

you should try to get refund/replacement from seller of whole motor since no way to tell if something else is in bottom somewhere

 

[bluck]

So I just contacted bekits and they are sending me a new top end. He recommended I fill the bottom end with half a cup of gas to remove metal bits. I was just using my other bike today and after a hill climb the motor was running good it was idling as I waited to make a turn and it just shut off. No big deal it shuts off sometimes after after idling. I go try to turn it on and doesn't turn on. I pedal home and decided to use the RT carb from the new motor to my old one (I rejet to 68) and still doesn't turn on but the float part of the RT carb is leaking gas as well I tighten it more and it leaks drops now. RT carb is awesome wish it worked as good as it looks. Choke won't work correctly once I Choke it doesn't unchoke. That's 3 motors down in 2 months last month I had another motor damaged from the piston and cylinder as well not as bad as this new motor. My current motor that just won't turn on today has about (~1,200 miles). Other motor from last month that had its top end wrecked for idk what reason full throttle, pop noise, doesn't turn on anymore (~500 miles). Yesterday's new motor (>1 mile).

 

[bluck]

Well, you're definitely in the market for a new top-end (like $35). It looks like a classic case of something very hard being pulled up through the transfer-port and getting wedged between the piston and cylinder-wall during the down-stroke. Clean out the case and see what's in there. It's also possible something got in there during the carb install, Check to see if the piston's lower ring's index-pin is still there; that little piece of steel is a likely culprit if it got loose. Since your combustion-chamber seems unscathed and if you're desperate, you could probably still run that top-end if the top-ring is still viable. Just clean up the piston damage, and remove the cracked transfer-port wall. Grind off any protuberances. You have my sympathy for a bad initial experience; these engines can be a crap-shoot, but when you've got a good one running well, it's all worth it. Going forward, I highly recommend disassembling and reassembling these engines yourself when you get them new. This way you can make sure everything's clean and properly assembled.

Seems about right since it was cracked but still running poorly after the second time I tried turning it on so it did work but both rings are now messed up. I didn't really disassembled this one because I was under the impression that bekits does that and installs better hardware(bolts, bearings). I did open the top end to make sure and it looked good. Also ran well before I changed it to the RT carb. Luckily it's not my first motor so I know how fun it could be but today man my other motor just won't turn on I am close to calling it quits and just purchasing the $500 ktm50 from dax. Just making builds with that more reliable engine. Or if I'm desperate a more reliable heavy 4 stroke.(would require learning all over again) but I like cruising at 34mph. Idk just 3 motors is too much to lose in 2 months. Also I have another motor ((I have a hoarding motor problem xD). It's in working condition. I will be replacing the magneto and cdi (one at a time) and checking it's it's that today or tomorrow.

 

[bluck]

Ok guys so I got a replacement cylinder this is the second cylinder on a new engine, it was also destroyed this time this long metal pin stayed stuck in th3 cylinder I will show a picture. Is this pin part of the crankcase as of now I feel the bottom end might be falling apart. Even thought the rod moves up and down like it's good hmmm does that look like a pin on the crankcase? I've never opened the bottom end is that something easily doable?

I also replaced the piston and Piston rings they were damaged as well along with this cylinder

 

[crassius]

that looks like the circlip that holds the wristpin in place - I'd guess you didn't get it solidly into its retaining channel

 

[bluck]

I thought that's what it was but they are still in place. Anything else everything was put on properly it's still a new engine.

 

[MotorBicycleRacing]

Ok guys so I got a replacement cylinder this is the second cylinder on a new engine, it was also destroyed this time this long metal pin stayed stuck in th3 cylinder I will show a picture. Is this pin part of the crankcase as of now

Is that the spring from your RT carb on the choke plate?

It isn't a circlip.

That piece of wire is not a part of your motor, probably was the
metal that destroyed your first motor then was still in the bottom
end waiting to wreck your new top end.

 

[bluck]

Is that the spring from your RT carb on the choke plate?

It isn't a circlip.

That piece of wire is not a part of your motor, probably was the
metal that destroyed your first motor then was still in the bottom
end waiting to wreck your new top end.

Are you talking about this sprig(in picture) because it's still there just took a picture. I'm baffled as to what it could be I did rinse the bottom end with gas maybe i didn't get everything. Would it be worth while to open the bottom end? Or does it require special tools/skills.

 

[Tyler6357]

The RT carb has a very thin gasket to keep the float from leaking. Make certain it is in the groove around the top of the float before putting it back on and tightening it down, it can easily get out of place when you have it off.

 

[BobbyT]

That wire looks exactly like the upper part of the choke spring in my SHA 15/15 carb. I use and recommend bekits. I haven't had any problems. Why did you change the carb?

 

[bluck]

The RT carb has a very thin gasket to keep the float from leaking. Make certain it is in the groove around the top of the float before putting it back on and tightening it down, it can easily get out of place when you have it off.

The gasket is still intact on the RT carb, I was able to solve my leak problem by untightening the bolts a tad bit.

 

[bluck]

That wire looks exactly like the upper part of the choke spring in my SHA 15/15 carb. I use and recommend bekits. I haven't had any problems. Why did you change the carb?

Yeah bekits makes top notch kits. I have ordered 3 motors from them, this is the engine that I started having problems with. I have built 7 bikes and currently have 4 motors just sitting not being used (not counting my ktm50 motor and the one on my red bike). Also a blown engine that was running perfectly fine and just decided to blow itself like this one(motor had 1,000+ miles). I changed the carb because the RT carb is said to be a tad bit better by some and with the better air filter and higher quality I thought I'll give it a go.

Btw which choke cable are you referring to? The one on the previous picture?

 

[bluck]

So I will be rebuilding the top end once more. My question is should I open up the bottom end? If so how difficult is that or even recommend? Or should I try to swirl the bottom end with a half cup of gas to get rid of metal bits that's might be stuck in there? (Which is what I did before this one blew and apparently there was something in there)

 

[sbest]

When in doubt, always open the bottom end up.
It is a 30 minute job with these motors, well worth doing for of mind.
Unless you don't mind buying yet ANOTHER top end and doing it next time?

Steve

 

[crassius]

I'm still thinking circlip - in the pic it looks like same thickness and seems to be lined up right where the circlip sits in piston

pics are hard to tell from, and circlips are fairly heavy to have come up from bottom, but there might have been two in the piston for some reason

it may remain a mystery - I'd disassemble that motor and keep it for spare parts

 

[bluck]

When in doubt, always open the bottom end up.
It is a 30 minute job with these motors, well worth doing for of mind.
Unless you don't mind buying yet ANOTHER top end and doing it next time?

Steve

Would I need special tools and also need to buy extra gaskets? I will try it first on one of my old blown motor that I use for spare parts

 

[bluck]

I'm still thinking circlip - in the pic it looks like same thickness and seems to be lined up right where the circlip sits in piston

pics are hard to tell from, and circlips are fairly heavy to have come up from bottom, but there might have been two in the piston for some reason

it may remain a mystery - I'd disassemble that motor and keep it for spare parts

I don't think it was a circlip as when I took out the piston it was only 2 and when I put the new one it only had two. The only reason I don't want to make this a motor just for parts is that I have 2 already that I use for parts I do not plan to have 3. Each spare parts motor is also of different types so I would actually like to save this one. I will give it one last go I will wash the bottom end with gas and swirl it 3 times. If I find out how to open the bottom end I will do so as well and after that I will just hope for the best if it blows then it most likely will become a spare motor sadly for such a new pk80 engine.

 

[sbest]

Would I need special tools and also need to buy extra gaskets? I will try it first on one of my old blown motor that I use for spare parts

You need the little threaded puller that comes with a new kit and a lot of patience the first time around. A complete gasket kit is less than $10 here in Canada. Don't pry or use excess force. Once you know what you are doing it takes less than an hour to remove the engine from the frame and completely disassemble it.

Start with a clean bench, have a container for small parts. Don't lose the ball bearing or buck bar. Take pictures and ask when you get confused.

Good luck!

 

[Slogger]

If it were mine I'd take off the top end and the magnet, get it to a part washing solvent tank and hold it upside down and use the solvent sprayer to wash out the bottom end real good.
I've never split the cases and don't really look forward to it.