10 mill ?

[kawiking]

my buddy has a 10 mill cub, got all the parts from k&t. he's had it about 8 months and now its blown up twice. first time we think it ran out of fuel (no pingel). it blew last sat. and pretty much blew the top of one of his pistons. my other buddy took it apart and said it looked like the crank seal went bad. they rode it all day sat and they said it didnt sound right on last pass, started it up when they were leaving and made a bad noise,it was blown. he hasnt been able to get in touch with k&t yet. has anyone with a 10 mill had problems with crank seals or pistons going bad. he wanted me to ask what kind of pistons do you run ?? he;s running a weisco piston.

thanks kawiking.

[FireHead]

I have had problems like that with alot of my engines (except for the Pingel thing)............ :biggrin:

[kawiking]

he knows a 10 mill has alot of hp.. and its going to put stress on the motor. its a drag bike , they are going to break. but he doesnt have alot of time on it so he kind of wanted to see what other 10 mill owners had/have problems with.

[PassionRE]

he knows a 10 mill has alot of hp.. and its going to put stress on the motor. its a drag bike , they are going to break. but he doesnt have alot of time on it so he kind of wanted to see what other 10 mill owners had/have problems with.

Did it blow the piston top out on the intake side or exhaust side?

[kawiking]

intake.... almost centered the 2 intake ports.

[dajogejr]

It's too lean...I did the exact same thing.

It was my fault, I got greedy...leaned down the pilot AND power jet big time...and I paid the price.

It cracked the top of the crown off on the intake side exposing the ring land.

 

I fattened it back up, flushed the bottom of the cases out with race fuel and benoil (my purge gas) and put well over 60 passes or so on it...and it's still going (cold, out of season now...)

 

Here's what he needs to check:

Is he running on alky or gas?

How much compression is he running? What is the squish? How much timing? What kind of carbs?

 

When I first built my 10 mil this year, I never checked compression....I had my machinist buddy cc the domes, 16cc.

So...I imagine my compression was around 240 give or take. Just a hair WAY too much for alky, two trips to the dunes, less than 10 passes each time and I was popping an O ring or backing out plugs...

 

I had a stock head cut to the same specs, 20 cc, gives me 175 to 180PSI, set my squish at .045 to .046, and aside from me getting greedy with leaning it out....my bike has run great and flawless all year long.

A set of pistons on my first year on methanol is not bad....

 

Here's what my piston looked like a few months ago: ( I Made a joke about being able to check ring end gap on the piston, finally...LOL)

 

 

[kawiking]

yep , thats what we are thinking. talked to him last nite and he said it was border line lean at l.s. 6 months ago and it got colder this weekend and that probably pushed it over the edge. he's running gas.....

[dajogejr]

yep , thats what we are thinking. talked to him last nite and he said it was border line lean at l.s. 6 months ago and it got colder this weekend and that probably pushed it over the edge. he's running gas.....

 

Any reason he hasn't switched it over to alky yet?

Just curious...

[kawiking]

not sure ?? i think he rather stay on gas for now. we are working 6 days a week and have barely any time to ride, so this being his second rebuild in 6-7 months i think alky is furtherst from his mind. lol !!!

[dajogejr]

not sure ?? i think he rather stay on gas for now. we are working 6 days a week and have barely any time to ride, so this being his second rebuild in 6-7 months i think alky is furtherst from his mind. lol !!!

 

 

I wish I had your problems.... It's too cold for sand tracks, and the water hasn't given a second thought about freezing yet...

 

I can tell you this, I need to move, put my bike in storage or quit smoking.

 

I don't smoke in my house, so out I go to the garage...light up...and just sit there looking at my bike.

 

Drives me absolutely nuts....

 

Let me know what I can do to help ya out....

[locogato11283]

blew my 10mm cub up at LS when we went. didnt know until i tried to get it running last weekend. i think a crank seal went bad or something. who knows. gotta tear the whole motor down now!

[kawiking]

my other friend took it apart and said that the crank seal was blow on his. they both said it ran good till it blew, i asked if they had oil coming out of the pipes and they said no. sucks u blew ur bike loco... seems like we always blow 1 or 2 bikes at l.s...

[BigRed350x]

I thought I blew a crank seal on my 10mm at sand mountain but it turned out to be sucking it through the square key on the primary drive gear on the crank, seal was fine. I've never seen it before and was befuddled when I put in a brand new key and still had the leak when I leak-down tested it. So I did what any respectable oil-field worker would do and gooped the square key up with hi-temp oil-resistant RTV shit and put it all back together. Pressure and Vacuum tested it at 20psi and it held fine. Ran it a couple times since then with no problems. Odd.

 

My cases are matched to my porting on my cub cylinders and I think the worst I've done so far is blow a base gasket. Well, besides the whole blowing it up once already. I pulled one like dajoger did and leaned it out. Now I run a pingle and a fuel pump and I'm getting different carbs with billet bowls this winter for it. Its def. fun to dune on though.

[Wildcardracing]

Make sure it's jetted right.

Give Kim a call at K&T (801)825-5870, He'll be able to give you a real good idea where the jetting needs to be with his porting. You could also email him at www.ktperformance.com, he's really good to work with.