Engine rebuild

[belly]

2000 banshee. FMF fatty/powercore II, stock carbs, tors eliminator, parking brake eliminated, stock airbox, 32:1 ams oil. Was tuning the carbs today and everything was running great. Got back from a test run and was letting it idle and then it started idling low. Tried to rev it up and bogged and popped from the right cylinder. Did a compression test and 80 in the left and 0 on the right. Brought it home and tored the top end down. (crank oil has about 15 min or run time on it. Fresh gas 91octane 32:1 amsoil, plugs were brown.)

 

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DIdn't see any scoring or grooves on the walls. the rings on the right were half there and half in the midpipe in pieces. As far as a rebuild, what do you guys recommend getting done? (besides pistsons, rings, bore, gaskets, etc... Would like to stay around $600 give or take. Might have to split the cases and see where the rest of the piston went to...

Edited November 8, 2010 by belly

[bansheesrtoys]

well you should aslo get a coolhead yours looks bad. as far as splitting the cases, i wouldn't just get a blow gun and blow out the crank lightly , don't blow out your seals. then spin it over and as long as it spin free and doen't bind you should be fine.

[Larry's Shee]

Don't think I'd chance a small piece not flushing out and blowing a bearing later. $20 for crank seals or $35 for all seals. Also could just get a stock head cheap. JMHO , your results may vary.

[Spidy]

Ok fellas what caused this to happen to Belly's motor? Looks like it was the right hand side. Mine has done the exactly the same thing to me 3 different times. Mind you it wasn't the same right hand cylinder all 3 times. The first time it happened I had just bought the bike. Figured, ok shit happens. Had it rebuilt and ran it for 2days and blew it up (right hand side again). Took it back to the builder, he gave me the run a round about my fuel mix being to lean. We argued about it cuz my buddy was running his kow on my fuel so I know that's not what happen or the kow would have been dead too!!

 

2nd build using my cylinders again ran for about 25 minutes and blew up the right side piston. Also trashed the crank this time.

 

3rd build was the HotRod 4111 crank (5m long rod 4m stroked) 2 new cylinders ported and polished. All this time were using Wiseco pistons. I'm sure they were stock in the first 2 builds. On this 3rd build using the HotRod crank we had to use the 795 Wiseco pistons do to the long rod setup. Ran fine a couple weeks, we even went out and drag'd it one Sunday, just beat on it keeping up with the bigger boys and there big carbs. (Mine are stock carbs lol). Went to ride with some friends the next Sunday... 15mins and blew a hole in the right side piston.

 

4th build is waiting for me to buy another set of 795's or some HotRod Stroker pistons designed to work with the HotRod crank. Before I put it back together I would like to hear some of your thought on what caused this issue for Belly and I. The only pieces that stayed the same in my story was the carbs and intake boots. I cant see any cracks in the boots but I bought new ones to install when I put the bike back together this time. I'm assuming an air leak somewhere..??? Will do a lead down test on it when I put it together. Thanks for any input!

Edited November 9, 2010 by Spidy

[belly]

I'll pick up a coolhead or something. compressed air will be used to get out the chunks/pieces in the case. Also, i'll pick up a magnetic drain plug and do some flushing to doublecheck for pieces. After looking at everything, i believe this is still the stock pistons. Probably order some crank seals since they are 10 years old. Now, there is a local shop that does machining. However, i wouldn't mind getting some port work done also. Looked at some of the site sponsers and it all looks like good work. Any recommendations?

[Larry's Shee]

A : drain plug is for trans not crankcase. B : aluminum is not attracted to magnets. C : Have to split cases to install crank seals.

[belly]

A : drain plug is for trans not crankcase. B : aluminum is not attracted to magnets. C : Have to split cases to install crank seals.

 

Thanks for the clarification. Been out of the quad scene for about 8 years. 2 strokes even longer. Think i'm going to send my stuff in to fastoys to get the bore done. appreciate the help.

[FASTOYS]

Spidy without pics its often hard to tell but i suspect after 4 times it's either lean jetting or an air leak. Need to do a pressure test!!

 

Belly, i would prolly sugest tearing complete motor down to check for contaminents (chunks of piston etc.)in the crank bearings etc.. Might check lower crank brg. too as it looks like it could be spreading apart from not being trued/welded...? Lots of times intake skirts break from Piston to cylinder tolarance being too loose and time for a rebuild has been exceeded.