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Post by 180°off on Apr 3, 2016 12:25:23 GMT -5
Put in New piston in 70cc bore kit. Thought I had tuned well. Soft seized on me already. Probably Fu#ked up everything once again! I think I'm done with 2strokes! Anyone want to but a 02 popcorn? And 2 kymco super 9's??? Let me know!
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Post by 'O'Verse on Apr 3, 2016 12:34:15 GMT -5
Might still be salvageable. I soft seized my stock 90 piston 3-4 times from heat. Small soft seizes.... Exhaust stinger was too small. Did you invest in a cht gauge for your build? Very important tool when modifying. Don't give up on 2 strokes yet.
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Post by stepthrutuner on Apr 3, 2016 12:58:03 GMT -5
Soft seizes usually are survivable with perhaps a small loss of compression. Best thing is to get some oil on the ring(s) and land(s) so any pushed up piston metal can work its way out from trapping the ring(s). I've had a couple that needed over night cool down before the motor would start.
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Post by frank50e on Apr 3, 2016 13:20:43 GMT -5
That really is explainable.Did you mic the piston and bore for clearance?That's really the only way to know if a new piston is being used in an existing cylinder.The CHT gauge would have alerted you for sure and is highly recommended on built 2ts.But as to the situation at hand your probably good.I personally if it were my own bike remove the top end.Make sure there is no aluminum stuck to the cylinder wall.Muriatid acid will remove any aluminum easily but must be handled carefully.Preferably outdoors.Then I would do a hand hone on the cylinder with 300 grit.Here's where my advice gets sketchy.As I said if was my personal bike I would do this but never on a customers or am I recommending this practice.I have a very fine file I keep oiled just for this.Study your piston to find where it stuck and gently file the mark away.Wash everything up with brake cleaner,dry then oil piston and cylinder up with 2t oil.Reassemble and keep an eye on the heat.
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Post by 180°off on Apr 3, 2016 13:34:41 GMT -5
No cht gauge. Didn't know I needed one. Don't even know what it's for? I guess I will find out now! When it has the 50cc it ran completely fine for about 2 weeks and then all of a sudden it started to soft seize. Ans then kept doing it. I dont understand why? Went from good to shit! In one day?
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Post by PIG on Apr 3, 2016 15:09:04 GMT -5
Probably got an air leak and leaned out.
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Post by frank50e on Apr 3, 2016 15:09:45 GMT -5
Jetting?
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Post by 190mech on Apr 3, 2016 15:46:49 GMT -5
Dude!Dont let a stupid simple machine beat you!!As the rest of the guys said,gotta be getting hot(CHT-cylinder head temp high,caused by an air leak(leaking gaskets or seals),or lean jetting(overheating and melting parts together)...Educate yourself,,and beat that machine!!!
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Post by ThomasTPFL on Apr 3, 2016 15:59:52 GMT -5
I didn't solidly snug down the valve adjusters on the kit I just installed and now one of them is somewhere inside the engine. I'm giving up on four strokes, too many parts to deal with!!!
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Post by moofus02 on Apr 3, 2016 16:11:07 GMT -5
I seized a snowmobile so bad it w was still locked up the next day. Oil and rocking it back and forth broke it free and it started back up. Low on compression but still ran. Seized from lack of oil (my fault)
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Post by 90GTVert on Apr 3, 2016 16:13:13 GMT -5
This forum would be pretty empty (actually never created) if we all gave up on our first soft seize. Myself and others have collections of messed up parts, 2T and 4T. If you can't deal with tuning problems or broken parts, the best bet is to buy a quality fuel injected scooter and just leave it alone other than maintenance or carry it to the dealer when it needs repair. Otherwise, chalk it up to experience/education/entertainment and move on.  Could be running lean, could be an air leak, could have something in the shrouds, could be higher than normal compression (squish or combustion chamber issue?)... just to name a few possible suspects if you choose to carry on with 2Ts. |
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Post by 180°off on Apr 3, 2016 16:18:19 GMT -5
Ok, so now I can't even get the thing to start. I guess I'll pill the head and take a peak and see if any major damage occured. I just wish there was someone close to me that could teach me about 2t. I love this forum but there is nothing like someone there teaching you how what where and y!
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Post by thatcrazyguy on Apr 3, 2016 17:04:04 GMT -5
Ok, so now I can't even get the thing to start. I guess I'll pill the head and take a peak and see if any major damage occured. I just wish there was someone close to me that could teach me about 2t. I love this forum but there is nothing like someone there teaching you how what where and y! When I joined this forum I had never opened up an engine, and now I'd call myself somewhat fluent with these 2t engines. I honestly just read every single troubleshoot post and replies and stored all the memory somewhere in my head lol. Give it time and a few more fuck-ups and you'll know these engines like the back of your hand!! |
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Post by tsimi on Apr 3, 2016 18:12:46 GMT -5
Don't know much info on your build but just slap on a BBK and done ain't the whole game. When installing the BBK make sure you put a thin film of 2T oil around the cylinder walls, needle bearing and piston. If you run it with your oil pump and not premix add a bit of 2T oil into the fuel tank, around 100:1 or even 80:1 for starters.
Then THE most important part is carb tuning. If you leave it in stock condition then your calling for a seize. Up jet, at least the main jet has to go up a couple sizes so that you get enough fuel and oil into the cylinder. Make sure you don't have any air leaks otherwise it would make carb tuning near impossible.
Aluminum BBK are usually not recommended for entry level 2T tuning they are a bit more sensitive than cast iron. CHT is almost a must have to control and tune a 2T additional to that a tacho.
We all have been where you are now but thanks to Brents tutorials and the guys here we all became better and better at this stuff. Failures are here to learn from so don't let them put you down. Learn from it and become better!
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Post by 2stroked on Apr 3, 2016 18:31:20 GMT -5
Shit... I think I have four or five soft siezed pistons on or under the bench. The tiniest damn air leak will sneak up and bite you in the arse as soon as you aren't expecting it. Follow the advice above. Maybe try a leak down test to check for air leaks. While tough as hell, these little 2t's can be sensitive, especially to air/fuel mix errors. How many miles did the bike have before you BBK'd it?? Check the crank seals.Maybe?  |
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