50mm bbk KABOOM!

[guen84]

I blew my 50mm bbk last night after a long WOT run, then went to cruzing speed. never looked at the temp gauge till it was to late. oops.... Question is what do i do now, had a cheap tiawan bore, looking to buy a better quality cylinder now, problem is my case is already milled to the larger boost port. Can i run a Polini? really want a good high rev cylinder this time.. Any suggestions????? signature has my set up..

[Trafficjamz]

I blew my 50mm bbk last night after a long WOT run, then went to cruzing speed. never looked at the temp gauge till it was to late. oops.... Question is what do i do now, had a cheap tiawan bore, looking to buy a better quality cylinder now, problem is my case is already milled to the larger boost port. Can i run a Polini? really want a good high rev cylinder this time.. Any suggestions????? signature has my set up..

Malossi has a larger boost port and works well with the ministroker.

What was the compression at on your 50mm ........to high of a compression and pump gas is a deadly combo

[guen84]

What was the compression at on your 50mm ........to high of a compression and pump gas is a deadly combo

compression was around the 130's, and i always ran 93 for that reason. gonna pull it apart today to see what happened, i do know the piston hit the plug.. the only thing i changed was moved ring on the needdle to the top... not sure if that caused it, but it was really running like crap in the middle

the regular 70cc molossi or you talkin MHR?? hows the boost port on the corsa???

[dun rite]

raising the clip to the top of the needle leans the mixture at 1/4 to 3/4 throttle. bummer about the blow up,

how did you break in the engine?

[veedubh20]

You can't run polini or Malossi bore.. Because boost bigger on 50mm jug. Did you use 50mm head? If not , The stock head cause to blow up, or base gasket thicken. Not set port timing right...

On the new bore kit, you don't go wide open throttle...... 1/4 throttle or less than half throttle. To break in piston. Rings.....

[SpreeMadness520]

this thread is scaring me

[guen84]

raising the clip to the top of the needle leans the mixture at 1/4 to 3/4 throttle. bummer about the blow up,

how did you break in the engine?

yes i know that leans it out but it would bog the cylinder in any other position, it actually bog at that position on occasion... break in i did heat cycles then bout 100 miles no more than 3/4 throttle, then came mini stroker and PG Long and rode the heck out of it!!! for 400 miles at least..

[dun rite]

well it sounds that you at least had fun. still a bummer..

[guen84]

You can't run polini or Malossi bore.. Because boost bigger on 50mm jug. Did you use 50mm head? Yes it was a 50mm head
If not , The stock head cause to blow up, or base gasket thicken. Not set port timing right... Thats a possibility checked before mini stroker not after.

On the new bore kit, you don't go wide open throttle...... 1/4 throttle or less than half throttle. To break in piston. Rings.....For how long are you suggesting??

[veedubh20]

400 miles riding, 150 mile up to 30 mph,,,, 300miles 35 mph . Til 400 , go wide open throttle n plug chop, tune jetting. Just go slowy on gas throttle when speed pick up n slow back off on vary speed.. I alway runs synthetic oil 2 strokes 32:1 , make the ring last longer, my red af18 has 72 cc polini contest a 5,500 miles not heat seize or scratch, cross hatch hone beautiful....

[guen84]

well finally got it apart, TrafficJamz is the winner compression to high... burned a whole in piston... cylinder looks pretty good still.. possibly try one of limp's 51mm ruima kits now.. any one have some feed back on them over a Molossi kit..

[Ricerider]

I burned up a ruima kit from limp. Feels like s*** and makes you nervous....

Scrap the ruima and get a malossi, I did 5 idle hot cold heat cycles, and didnt go over 1/4 throttle for two tanks of gas.
I have over 500 miles and no problems. Crusin at 50mph it runs 280-290f....

I have had it up to 61.2 on a gps but didnt hold it there... I let off at 320f


I am not saying the ruima is a bad cylinder but you get what you pay for....

Anything over 72cc has a very thin cylinder wall and gets hot quick

The malossi kit pulls nice and has plenty of power. Half throttle from a stop light and just pull away from traffic

[guen84]

rice thanks for the input... i will deffinetly keep that in mind... what happened with the Ruima kit???

[bakaracer]

I burned up a ruima kit from limp. Feels like s*** and makes you nervous....

Scrap the ruima and get a malossi, I did 5 idle hot cold heat cycles, and didnt go over 1/4 throttle for two tanks of gas.
I have over 500 miles and no problems. Crusin at 50mph it runs 280-290f....

I have had it up to 61.2 on a gps but didnt hold it there... I let off at 320f


I am not saying the ruima is a bad cylinder but you get what you pay for....

right here is nonsense talk. its not the cylinders fault it blew up. ruima bores will work at over 400deg. I ran mine to 435deg in a race at wot for over 1/2mile down the straight when the temps were already above 400deg and won. so dont blame the bore.

[bakaracer]

well finally got it apart, TrafficJamz is the winner compression to high... burned a whole in piston... cylinder looks pretty good still.. possibly try one of limp's 51mm ruima kits now.. any one have some feed back on them over a Molossi kit..

if the cylinder walls are not scored up then just get another piston and rings. this time lower the compression even more. 93 octane will support about 9.5to1 compression on 2 strokes. if its higher than that then expect engine knock at high rpm's. Oh and the malossi or polini bore will NOT work on your block since you cut the boost port to fit the ruima one. you either have to fill it in with epoxy or aluminum.