How often should you rebuild the top end?

[OhioLT250R]

Hey guys, I was just wondering how often you rebuild your top end. I just ruined my motor and I think it could have been prevented if it had been rebuilt.

[Smokin'Gun]

I rebuild mine at the first sign of power loss.

[lannyLT250R]

yea, i think that if you rebuild before it dies, you'll prolly save alot of damage done to things and having to replace more than a piston and rings...

[OhioLT250R]

Yeah, my motor is now shot. I talked to my friend who works on motors and he said that it looked like the piston was a bit loose and it caught an edge on the exhaust port and tore itself apart. So you just do it when you lose power. Does anyone else have any other suggestions like ex> every 50 hours or a rough estimate of how many hours of use you can get before needing a rebore?

[Flattrack]

Do your self a favor and invest in a Compression tester and if you like to tinker around build a leak down tester. Those two items are the proverbial gods.

Do periodic checks of the motor. This will tell you more than the seat of the pants feel. I do a leak down and Comp. test before I ever run a fresh motor.The leak down will tell if you have any air leaks that could cause a lean condition. The comp. test will give you a base line to compare to later

I check comp all during break in. When the poundage peaks out and then levels off you know that motor is broke in completely. I check Comp. numbers every 10 hrs of run time or so to make sure the piston rings and Cyl wall are a good match and not loosing compression. I rebuild after 10-20 Lbs of lost compression.

It depends on the type of riding. The harder I ride the less time i give between inspections. When we race I check after every race then I know what I have to do to the motor leave it alone or pull it apart I only give them 5 lbs. lost before I'll pull it apart. For every day riding Every 10 hrs is fine. I do leak down test about every 20-30 on every day riders. This lets me check all the critical areas that might pull in air and cause a leak, Crank seals and gaskets.

This is what i use for a indicator of when to rebuild. I have also had motor take a shit with no indication at all but I usually catch it before that happens.

[nickxc]

Originally Posted by Flattrack

Do your self a favor and invest in a Compression tester .

Thats for sure. I dont have a leak down tester but I would like to get one how do you do it???

as for the question here. I keep tabs on my compression all the time. I had my motor done in march and rode all summer and all fall on it and I ride about 4 days a week on average. I used 4 gallons of oil at 32:1 so I burned 32x4=128 gallons of gas and I havnt lost one single pound of compression all summer. Im at 135 in both cylinders and they are as close to perfectly exact as they can get. I always use amsoil dominator and I ride this thing hard for long periods of time at wot and I really rip on it. at this rate I will get several summers out of my motor. Its all up to you. if you notice power loss or if you have a compression tester and you start to loose compression then rebuild. if not just ride it and take care of it. and use a foam filter and your rebuilds will be much much less frequent...

[lannyLT250R]

I was wondering where i could find a compression checker. and what do you use for the leak down thing? I haven't heard of that before. I'd like to check my compression though.

[nickxc]

Originally Posted by lannyLT250R

I was wondering where i could find a compression checker. and what do you use for the leak down thing? I haven't heard of that before. I'd like to check my compression though.

compression tester= sears $17

I dont know about a leak down tester but I have heard of it and would like to be able to do it also...

[Banshee]

MacDizzy has instructions on how to build one I think. Also Motion Pro I think has the best one out there becasue it fits most every 2-stroke but it cost like $250.

[nickxc]

Originally Posted by Banshee

MacDizzy has instructions on how to build one I think. Also Motion Pro I think has the best one out there becasue it fits most every 2-stroke but it cost like $250.

is that macdizzy.com?? are they easy to build. Id rather build one then buy if I can...