how many runs before overhaul?

[georgie]

After how many runs on the 1/4 mile run before it's time for a motor tear down and overhaul? Average runs.

[Tedder]

After how many runs on the 1/4 mile run before it's time for a motor tear down and overhaul? Average runs.

 

I run 1/4 mile. My alcohol motors beat the hell out of the intake side of the pistons in one season. Pistons in our gas motors are good to go for years.

I tear down after every season to inspect them.

[dragbanshee98]

i dont run 1/4 mile, but i do run 300ft sand. been 4 years now since a rebuild. first and second year i ran a dozen races both years with about 5 classes per race with nearly 50 passes each race. last year i only ran 3 races so about another 200 passes. i would say if ur on gas ur motor would last half of what a 300ft motor would. if everything is durable like it should be.. i always tear the carbs and exhaust off each spring and check compression just to be sure.

[SlowerThanYou]

After how many runs on the 1/4 mile run before it's time for a motor tear down and overhaul? Average runs.

 

Listen to the guys that actually run at least 1/8 mile. There's only a few that run 1/4 successfully fast & Tedder has replied already. Nothing against the 300', but the stress on the motor is less severe & I've done both.

 

Now to answer your question. We need to know what fuel, oil & oil ratio you are using. Plus, your shift rpm & what rpm it goes thru the traps at & some basic motor information.

 

We baseline our motor when new & broken in with a compression check. We then use that baseline when checking compression throught the season. We use that as an indicator to ring & piston problems.

 

As for the crank, we look at replacing or rebuilding around 400 runs. Our 1st crank (cast 7mm) got 450 runs before the lower rod bearing cut loose. That crank was primarily run on alky with around 75 passes on race gas.

 

Our current crank (billet 7mm) has around 300 1/4 mile passes. OOPS got to run, I'll finish later.

[georgie]

Listen to the guys that actually run at least 1/8 mile. There's only a few that run 1/4 successfully fast & Tedder has replied already. Nothing against the 300', but the stress on the motor is less severe & I've done both.

 

Now to answer your question. We need to know what fuel, oil & oil ratio you are using. Plus, your shift rpm & what rpm it goes thru the traps at & some basic motor information.

 

We baseline our motor when new & broken in with a compression check. We then use that baseline when checking compression throught the season. We use that as an indicator to ring & piston problems.

 

As for the crank, we look at replacing or rebuilding around 400 runs. Our 1st crank (cast 7mm) got 450 runs before the lower rod bearing cut loose. That crank was primarily run on alky with around 75 passes on race gas.

 

Our current crank (billet 7mm) has around 300 1/4 mile passes. OOPS got to run, I'll finish later.

 

I'm running 111 oct. klotz and 4oz. to a gallon mix.

Motor

392 cub. 39 pwk's, vforce 3 reeds, 1-4 5/6 m duneable tranny, lock up with soft springs, shearer's oof pipes, stock cdi, coil, stator and flywheel.

Cranking comp. new is 160, Present comp. haven't checked it yet.

I used to run high 11's at 103 mph, now 12 flat or 11.9 at 100 mph. Which is why I'm thinking I should just tear in there and change out the seals. I've got more then at least 160 runs on this motor.

sorry i don't know what rpm's I'm at going through the traps, I'm the only one on this side of the pacific ocean that races a quad on the 1/4 mile.

Thanks a bunch for the replies.

[SlowerThanYou]

Our current crank (billet 7mm) has around 300 1/4 mile passes. OOPS got to run, I'll finish later.

 

Finishing up. Our current combo with the billet crank Was torn down, inspected, new crank bearings & new seals put in Mar. 2010. All the hard parts crank, piston, rings, nickasil, domes, & tranny have around: 300 1/4 mile runs, 90 hill shooting runs & 90 300' sand runs. I'm not to worried about the motor & plan to run it 300' for this year & possibly next year.

 

Now, with you only having around 160 runs. If it was my motor, but it's not. I wouldn't touch it. You have to make that decision for yourself. You know your quad better than I.

 

Our current conbo has been ran on minimum leaded 110 octane race fuel @ 40:1 with Klotz Supertechniplate.

 

If you have any more questions ask away.

[camatv]

i didnt read all that up there.

 

BUT tear it down whenever you ahve a few weeks or months of down time if it lives. maintenance is much easier on a running motor instead of a broken one.

 

a proper tear down woudl include crankshaft inspection. and possibly even disasembly and inspect bearings etc

[banshee760]

I would do a leak down and compression check if that all checks out good then if u have the actual time to tear it appart i would check the bearings on the crank n so.... u should also check ur clutch maybe it slipping a litle bit at the end and maybe thats why u r losing that 10th of a second

[camatv]

my 535 is going into its 6th straight season on teh same crank, pistons, cyl and plating, head and transmission, shift forks etc.

 

its on its 3rd basket, 2nd clutch and 3rd set of cases.. let alone numerous base gaskets from blowing the cylinder off the cases. hardend custom studs fixed that issue....

 

my wife's old 350 got new pistons and a fresh bore after about 2 1/2 years of dunning and racing and trail riding. and she would race it till it ran out of gas. then get more and go back out.. its now on its new cylinders and same lower end/ crank. this willb e its 4th year on all that..

[sleeper06]

I'm on year 4 with a 1/4 mile motor it's on alky now psi has dropped 3 since I built it so I might do rings this year and pressure test is still tight as a clams ass,as long as it was built tight. You should have no worries

[421alkybanshee]

ive got 1 season on my 421, probably have 100 runs on 1/4 mile and no problems here.

[camatv]

its funny to me to watch the fart can bikes explode all the time and know that i have the same old junk inside my motor.. im sure i'd do do my pants if it had an hour meter on it.

[georgie]

I would do a leak down and compression check if that all checks out good then if u have the actual time to tear it appart i would check the bearings on the crank n so.... u should also check ur clutch maybe it slipping a litle bit at the end and maybe thats why u r losing that 10th of a second

 

Changed out the clutch and back in the 11's again. Clutch was slipping a little bit.

[georgie]

its funny to me to watch the fart can bikes explode all the time and know that i have the same old junk inside my motor.. im sure i'd do do my pants if it had an hour meter on it.

 

Lol.