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Discussion Starter · #1 ·
I have a 87 honda trx250x and i am having problems installing my new stage 1 camshaft. When i first installed i got all together and as soon as i turned over the motor i bent both intake valves. They did not hit my piston and dont look like they hit each other. I am curious to if you think my timing was off or what? Im not sure which top dead center mark to go by and does it matter. I know one mark is top dead center on compression and the other for exhaust tdc. And pretty sure my timing marks were accurate on the camshaft gear. I am getting my head worked on now with all new vavles and springs. Also cleaned. Just dont want this to happen again when i get the head back and ready to install. Would love some suggestions to see if i messed up or what happened
 

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Welcome to the forums. The position of the cam determines the stroke when on TDC. So, align the "T" mark on the flywheel with the mark on the case and the piston will be on TDC. Now, make sure the lobes on the cam are facing down and you will be on the compression stroke. The compression stroke is the stroke you want to be on to set the timing.
 

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Discussion Starter · #3 ·
Well does spark go off the camshaft or crank. So spark is at tdc compression stroke. So can it be mixed up/
 

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Well does spark go off the camshaft or crank. So spark is at tdc compression stroke. So can it be mixed up/
You are setting the cam timing, not the ignition timing, so spark doesn't have anything to do with it. There are two marks on the flywheel, a "T" mark and an "F" mark. You want to line the "T" mark up to set the cam timing. The "F" mark is just the point when the ignition fires. Don't pay any attention to the "F" mark.
 

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Discussion Starter · #5 ·
Ok thank you. What do you think happened may to bend my intake valves? I thought maybe when i installed the clylinder head cover that holds the rocker arms. Maybe i jammed something to cause the rocker to bend the valve. Or would it just be timing?
 

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If the piston didn't hit them, I don't know what would have bent them.
 

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Discussion Starter · #7 ·
Ok. Have any jetting sugestions? I know it will run lean after i get everything together. So got any suggestions where to start?
 

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Moose would be the best person to ask about the jetting. Are you just adding the cam, because just adding a cam won't make the engine run lean.
 

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Discussion Starter · #9 ·
Im adding a cam and fmf full exhaust. Figured it would run lean after both of them
 

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Im adding a cam and fmf full exhaust. Figured it would run lean after both of them
The cam won't have anything to do with it, because the air is already mixed with the fuel by the time it gets to the valves, but the fmf exhaust will flow more air so it will be leaner and you'll have to go up on your jet size. I would also consider an aftermarket air filter with the exhaust, if you don't already have one. Jetting is more of a trial and error process, but Moose (trx2five0) is good at guessing pretty close. I would ask his opinion about the jet size.
 

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sorry I'm so late on this topic..lol Helmut is correct on the cam and lean/rich issue, you will only be allowing a little more flow though the head but with exhaust and filter you will need to rejet. ok a stock main jet is 128 and 35 slow jet on the 250X adding the exhaust and filter bump the main up to a 134 pull the air box cover off, back the air screw out 1/2 turn. If you get a sputter when you shift to 2nd and just barely crack the throttle you can bump the slow jet up to a 38 also the throttle cable adjustment will play a role in that sputter as well make sure you check the slack at the carb. remove the big black cover and put your thumb on the throttle barely start to crack the throttle if the thumb moves more than 1/4" back the cable out of the top of the carb about 2 turns. Keep us posted. By the way ATV Parts, ATV Tires, Dirt Bike Parts & Motocross Gear | Rocky Mountain ATV/MC sells the indavidual jets, it's alot cheaper than buying a kit with a bunch of needless jets in it.
 

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Discussion Starter · #12 ·
yah i have a k&n filter but thanks for the input man. ill ask him about the jetting
 

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Discussion Starter · #13 ·
thanks MOOSE. yah im just waiting to get the head back from machine shop and then putting back together. im gunna get them jets tonight. do you have any idea what i did to bend both intake valves after installing everything? i just dont want it to happen on me again u no?
 

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If you bent the valves when you were trying to start it you had the timing way off and the piston smacked them when it was at TDC be sure you check and double check when you put you timing chain on the cam gear and have you timing marks lined up at the right marks
 

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Discussion Starter · #15 ·
I thought they might have hit the piston, but there was no mark in the piston at all. Not even scuff mark from removing the carbon off the top of the piston. Idk. And i triple checked the timing and it looked perfect
 

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The piston hitting the valves is the only thing that I can think of that could have bent the valves, but I don't know why it wouldn't have a place on the piston.
 

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Discussion Starter · #17 ·
K thanks. Yah idk what happened but i mite have had the timing off but i dont think i did. I gunna take more time on the timing next time
 

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Just line the "T" mark up and make sure the lobes on the cam are facing down when you line the marks up on the cam gear and it will be in time. After you put the tensioner back in, check the timing marks again to make sure nothing moved.
 

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Discussion Starter · #19 ·
Ok thanks man. Well ill let you guys no how the istall of everythign goes. Thanks
 
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