Engine Trouble newby with power loss prob

[swamprat]

this is my first venture with a motorized bike but not with 2 stroke engines as have been playing and racing outboard hydroplanes since the '70's but i'm getting old.....er.....and decided to put a motor on my bike. now that i have it broke in i went for some speed spurts. the prob is that it runs ok [all china crapynes conciderd] for about a minute or so then it suddenly slows way down. in the outboard engines [2 stroke] this means to lean most of the time. so i played with the needle. no good. i opened up the jet a little bit. motor lost some power and speed but no affect on the main prob. before i get all wrenchy or throw the thing in the lake i thought i would run it past you guys. btw this only happens at full throttle.

 

[crassius]

I've seen this with too much vibration causing the fuel to foam in the bowl. Are you seeing a lot of bubbles in the fuel line?

 

[swamprat]

haven't looked at the feul line but omg does the thing viberate at top rpm. will check it out now. back in a few

 

[swamprat]

sure enough. bubbles

 

[swamprat]

geeze! just wanted to ride the thing awile before tore it down and blueprinted and modded it. after all stock is for no fun. lol

 

[crassius]

you didn't mention if you had finished running in the engine yet - for the first couple hundred miles you shouldn't go much over 1/2 to 3/4 throttle - later, the engine will smooth out quite a bit

for now, check that the engine is mounted tight to the frame, as that will dampen some vibration & check that intake & carb are tight

 

[swamprat]

im at the end of the break in period where i can open it up for spurts. that's when the prob showed up. i checked the engine mounts and they where loose. i also need a o-ring for the carb. there are several upgrades i would like to do to make it reliable. more power comes later after other motor projects.

 

[StrontiumEthics]

Loss of power usually indicative of air leak.
Check the head and make sure its torqued down look for ANY kind of leak. I had this happen before also.
Make sure your carburetor float adjusters actuate to prevent Carb overflow
Tighten All bolts especially around intake.
Definitely do a spark plug test to see what your mixture looks like! (Post pictures if you can)

 

[geebt48cc]

Yeah, sounds like the o-ring could be one of the answers. Also, keep head torqued too...............(all nuts and bolts for that matter)

 

[rawly old]

My advice, unless you enjoy having to constantly tweak
your engine, spend the extra money and get a Tanaka PF
4000. the 7 yr. private use warranty sez it all. If you want
performance & reliability don't waste your money on cheap
garbage. I've been through a lot of engines and I know
whereof I speak.