Seized :(

[Zippy77]

Well about 3 months after modding out my 50cc 2 stroke BWS to a 70cc with a big bore kit, high performance exhaust, lighter roller weights, carbon reeds & proper sparkplug... She went and seized on me the other day and won't start ever since . btw I think it seized because I forgot to switch to 100% synthetic oil & I was advised to also add a cap of oil to gas tank and I didn't do that either:( Just wondering, what parts exactly will have to be replaced??? Thx!!

[Zippy77]

*Also yes I did put in 3 uni air vents

[usmcdoc]

Sept 1, 2014 21:08:16 GMT -5 Zippy77 said:

*Also yes I did put in 3 uni air vents

Sounds like your problem right there...the extra air made it lean. Synthetic oil is not a necessity for a 2 stroke BBK..in fact worked on a guys Eton Beamer that had a BBK with 14,000 miles on it. All he ever ran in it was Chain Store brand 2 stroke Dinosaur oil..never tried a drop of synthetic. Also did you upjet and increase your main jet size over the stock one? I have seen many not do that..but then they only get about 5 miles before a seize..

[Zippy77]

Sorry forgot that too....upgraded original jet from 90-100

[moofus02]

Did you ever change gears in that? How fast were you running and at what rpm? What do you have for compression? What does the cylinder and piston look like? Don't know what you need until you know what you hurt. That will give you insight into why it blew up so you can correct the problem. Poor quality oil, lean mixture etc. Do a compression test pull the top end and post pics. Might just need a cleanup and a new piston. Those cast iron cylinders are tough. If you are still running the stock gears you need to change gears while you are down. Just my guess but my 2 cents you were lean somewhere

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[usmcdoc]

In my opinion and the opinion of many others on here..a UNI or free flow filter has no business on a 2 stroke. Reason why? 2 strokes don't like lean...the free flow air filters make them hard to tune..and of course..well..I have seen them cause too many 2 strokes to soft seize. If you are getting enough fuel/air from a stock or slightly modified airbox..what performance gain can you get from a free flow except more air? Part of the lubrication for a 2 T is from fuel..so if you give it more air..you rob the engine of some of its lubrication via less fuel to the engine.

Also I agree 100% with what moofus02 said above.. Yup he is right Sir..

[moofus02]

If you were still screaming that with stock gears you are way past the rpm the pipe and cylinder are designed for. Even if it is jetted right it might go lean in the over rev

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[usmcdoc]

Sept 1, 2014 21:45:04 GMT -5 moofus02 said:

If you were still screaming that with stock gears you are way past the rpm the pipe and cylinder are designed for. Even if it is jetted right it might go lean in the over rev

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This is true also. My Adly with a BBK and Tecnigas Next R would run great!!..BUT go lean when the rpm's hit 10k..but by then I was hitting 60mph and I never rode that fast anyway. Well unless it was brief such as when passing a 150cc Scoot just for fun. But it was only a brief few second run at 10K.

[Zippy77]

Sept 1, 2014 21:39:47 GMT -5 moofus02 said:

Did you ever change gears in that? How fast were you running and at what rpm? What do you have for compression? What does the cylinder and piston look like? Don't know what you need until you know what you hurt. That will give you insight into why it blew up so you can correct the problem. Poor quality oil, lean mixture etc. Do a compression test pull the top end and post pics. Might just need a cleanup and a new piston. Those cast iron cylinders are tough. If you are still running the stock gears you need to change gears while you are down. Just my guess but my 2 cents you were lean somewhere

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Ya I'm still runnin the stock gears but I have the new ones on the way. I typically go 60-70kph at fastest.

[moofus02]

That would put you in the over rev range it could be lean there. Depending what it looks like a hone and piston might cure it

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[2TDave]

Moofus and Doc are right on here! What did the plug look like after the seize? As said pull it apart and post some pics.

[2strokd]

Still running oil injection? Stock carb? Those both can play a big factor!

I agree somewhat with whats been said, but please know open filters are just fine to use on 2T,s IF it is tuned proper for it. I personally dont like the noise they let out. Its like having an intake and piped exhausts lol.
If you are using a stock carb its pretty hard to get them dialed in with an open filter unless you have slides and needles with jets. Better off with a bigger better carb with a 70cc IMO. Even then you will still need some tuning, maybe a needle swap etc.

I agree with taller gears in a Zuma for sure! You could have some real short 14,s in that thing now. Makes for a screamer!

[rpmcycleservice]

Also, would be a good idea to open up the carb and check for sediment in the bowl.....I have had bikes in the shop the past few years where you would get a partial blockage of the main jet from trash in the gas.....

[rpmcycleservice]

Also, would be a good idea to open up the carb and check for sediment in the bowl.....I have had bikes in the shop the past few years where you would get a partial blockage of the main jet from trash in the gas.....

[moofus02]

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