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Old 04-18-2013, 10:40 AM   #1
Zane Neher OP
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TDC/valve adjustment

This is for a 91 dr250.

It's been a good while since I've done this and it was on an ironhead, so I was dealing with pushrods and the such.

Anyway, the basics is to find TDC on compression stroke and call it good to adjust to the required specs.

Could I just hit the highest gear, toss a straw in the spark plug hole and once it maxes out at the top, call it TDC and adjust, or is it a little more complicated?

I'd have a manual but appearently UPS is having issues with finding where I live, so now Im waiting for it to arrive at my work. Im getting some top end noise on the right side of the motor and since Ive yet to do a valve adjustment, Im hoping that's it.
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Old 04-18-2013, 10:42 AM   #2
Adam R
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Originally Posted by Zane Neher View Post
Could I just hit the highest gear, toss a straw in the spark plug hole and once it maxes out at the top, call it TDC and adjust, or is it a little more complicated?
As long as it's on the compression stroke - yes
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Old 04-18-2013, 12:11 PM   #3
Birdmove
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Yes, that would work. Royal Enfield even makes a tool that goes into the spark plug hole. It's gat a plunger. You just rotate the crank till the plunger is at the highest point and that is TDC. Then, to be sure you are on the compression stroke, try wiggling the rockers. They should both have play. If there is no play in one rocker, rotate the crank one revolution back to TDC and recheck for play. Both valves must be closed with play at the rocker, or a gap at the valve where the shim is, depending on what type of adjusters your bike has.
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Old 04-18-2013, 12:13 PM   #4
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Then, to be sure you are on the compression stroke, try wiggling the rockers. They should both have play.
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Old 04-19-2013, 06:51 AM   #5
Zane Neher OP
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Guess Imma venture out there and see what I break.
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Old 04-19-2013, 11:01 AM   #6
Buliwyf
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You don't have to be exactly at TDC to set the valves. The valves are loose and closed for a bit of piston travel and cam rotation.

Crank her over till both valves close completely and then a little more. Check valve lash, then crank the engine over by hand some more to make sure it takes a while before the valves open.

I think my Honda even has a visual timing mark.

I've been skipping valve adjustment procedures and doin it this way on diesels for years. But on gas engines and some bike engines there may be a procedure that makes no sense, but works really well. (Ex. GM 454)
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Old 04-19-2013, 11:23 AM   #7
Zane Neher OP
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I turned it over until I got the most pressure coming from the plug. Seems that TDC where the rockers would rock and the other TDC they were pretty firm. Open/close I guess you would say.

Started the bike, nothing exploded.
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Old 04-19-2013, 12:34 PM   #8
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Seems to ride better, but does the idle normally change when you do the valves? Seems mine went down a good bit.
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