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stevemcqueen1968

DR350 issue with valve clearance and decompression

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Hi everyone, 

I recently got a 1990 DR250 that had the engine swapped from a DR350, presumably 90-93 model.

It was missing the decompression lever and cable, and the previous owner used it that way. I put on a decompression lever and cable, then adjusted the valve clearances.

My problem seems that either the decompression lever will work and become engaged by the lever, and click back when it hits TDC but with no compression overall, or I have high compression but the decompression lever does nothing.

Ive tried to adjust the exhaust valve to the manual spec and even play around with increasing or decreasing the clearance.

So it seems either I can kick it with no resistance and no combustion, or nearly impossible to kick but a sputter hear that it wants to start.

Am I doing something wrong, or am I missing something?

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22 hours ago, Tekime said:

Are you 100% sure you did the valve adjustment at TDC on the compression stroke?

It's been a while since I've done any motorcycle work and I've never done a valve adjustment before, so I wouldn't say I'm 100% sure. But I did follow the instructions from the Clymer manual and another online resource: http://ridersrecycle.com/blog/valve-check-and-adjust-suzuki-dr350/

I took that stator cover off and rotated the rotor until I could see the T mark in the timing hole, and made sure to check that there was some play in the rocker arms to verify it was TDC on the compression stroke.

Oh, and now an unrelated (or related) issue is there's a faint grinding noise when I rotate the rotor after TDC on and a fair amount of resistance, even with the spark plug removed. Maybe the camshaft is rubbing against something, or debris in the cylinder fell into the spark plug hole? I'm kind of afraid to try to get it started now lest I do some damage.

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19 hours ago, stevemcqueen1968 said:

It's been a while since I've done any motorcycle work and I've never done a valve adjustment before, so I wouldn't say I'm 100% sure. But I did follow the instructions from the Clymer manual and another online resource: http://ridersrecycle.com/blog/valve-check-and-adjust-suzuki-dr350/

I took that stator cover off and rotated the rotor until I could see the T mark in the timing hole, and made sure to check that there was some play in the rocker arms to verify it was TDC on the compression stroke.

Oh, and now an unrelated (or related) issue is there's a faint grinding noise when I rotate the rotor after TDC on and a fair amount of resistance, even with the spark plug removed. Maybe the camshaft is rubbing against something, or debris in the cylinder fell into the spark plug hole? I'm kind of afraid to try to get it started now lest I do some damage.

Sounds like you probably had it right. I usually remove the spark plug and visually check the piston while I watch the valves open and close just to be 1,000% sure. Soon as the piston hits TDC after the intake valves close I know it's at TDC on compression.

I would definitely hit pause and investigate that noise and where the resistance is coming from. There should be little resistance with the plug removed. These bikes make all kinds of noises but grinding is usually not a good sign! I'd just start by pinpointing where the noise is coming from, and getting as much light as possible into the cylinder to visually inspect. Maybe you'll get lucky and find something obvious, but you might be in for popping the valve cover off entirely and inspecting. Would be a good opportunity to inspect the timing as well - I think it's possible to set the cam 180deg off and still have a running (but entirely wacked out) motor.

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Posted (edited)
3 hours ago, Tekime said:

Sounds like you probably had it right. I usually remove the spark plug and visually check the piston while I watch the valves open and close just to be 1,000% sure. Soon as the piston hits TDC after the intake valves close I know it's at TDC on compression.

I would definitely hit pause and investigate that noise and where the resistance is coming from. There should be little resistance with the plug removed. These bikes make all kinds of noises but grinding is usually not a good sign! I'd just start by pinpointing where the noise is coming from, and getting as much light as possible into the cylinder to visually inspect. Maybe you'll get lucky and find something obvious, but you might be in for popping the valve cover off entirely and inspecting. Would be a good opportunity to inspect the timing as well - I think it's possible to set the cam 180deg off and still have a running (but entirely wacked out) motor.

I was working on it today and I figured out it was just the camshaft on the rocker arms, I have rotated the rotor so many times without it running and getting oil that it was making a scraping noise and giving resistance from lack of lubrication.

I went ahead and adjusted the exhaust valve to .13mm but no joy on being able to use the decompression lever. I actually got it started and went around the neighborhood. I came back and shut it off, and now it won't start again after sitting for only 30 minutes or so. Usually I'll get a little kickback from the kickstarter letting me know it wants to start up, but nothing now. Maybe it's flooded now? I did try starting with no choke and a little throttle a few times.

Edited by stevemcqueen1968

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I'm gonna replace the ignition coil, it looks like it's a little bit out of spec and I think maybe it's causing an issue when the bike warms up. Looks like the spark is weak and orange colored, so I'm guessing maybe that's part of the starting issue.

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Right on. The decomp lever is weird - are you adjusting it after the valve adjust and still not working?

Hot start issues are common, and usually come down to jetting, setting idle screw correctly, proper exhaust & air flow. My bike used to struggle to no end with hot starting on the trail, but after a proper carb setup, perfect valve adjust & idle screw setting it will start in a few kicks hot or cold. Took ages to get it dialed in though!

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Posted (edited)
29 minutes ago, Tekime said:

Right on. The decomp lever is weird - are you adjusting it after the valve adjust and still not working?

Hot start issues are common, and usually come down to jetting, setting idle screw correctly, proper exhaust & air flow. My bike used to struggle to no end with hot starting on the trail, but after a proper carb setup, perfect valve adjust & idle screw setting it will start in a few kicks hot or cold. Took ages to get it dialed in though!

Yeah, I'll adjust the valves first then the decompression lever. But I'll make sure that there's no clearance between the lever and the boss on the cylinder head. Here's a quote from the Clymer manual:

"On models so equipped, check the decompression lever clearance as described in this chapter. If the clearance is incorrect, loosen the locknuts and turn the adjuster until there is no clearance between the lever and the boss on the cylinder head cover. This will ensure that the lever shaft is not touching the exhaust valve rocker arm."

The thing is it seems like the only way for the decompression lever shaft is not touching the exhaust valve rocker arm is to remove it completely. Otherwise it'll always be applying some level of pressure and pushing down on the rocker arm.

And yeah, I'm in the same boat of getting it dialed in. I bought it from a guy that only had it for a few months and didn't do anything with it, so I'm only going on what he said he was told from the owner before that. It has the air box mod on it with holes cut in the top, and supposedly the carb rebuilt/rejetted. It's kind of a Frankenbike in that it's a DR250 with a DR350 engine, aftermarket FMF exhaust, modded air box with a rejetted carb and a Baja Designs street legal kit on it with an cheap aftermarket Chinese headlight. And it seems like it wasn't really taken care of that much—the air filter wasn't even screwed in and was just sitting in the bottom of the air box, there was no gasket on the oil filter, it was missing the gaskets on the crankcase covers and I'm pretty sure gasoline had seeped into the oil.

Edited by stevemcqueen1968

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I replaced the ignition coil so I think that should be helping. I realized too that the there are 8 wires coming from the magneto and only 6 are being used. There's a connector with 4 wires in it that I believe are for both pick up coils, but only one of them can be connected to the CDI. I think I may have switched the wires to use the wrong pick up coil for the ignition, so I fixed that.

Now the bike is showing signs it wants to start again, but in a bad way. I'm getting massive kickback from the kickstarter again. I was able to tighten up the exhaust valve enough to be able to use the decompression lever, but I think it may be a little too tight.

Could the bad valve clearances cause the kickback in the kickstarter, or would it be a timing issue?

Or bad kicking form? I've read a lot about the starting procedure and I use the decompression lever, let it pop out to signify TDC, take the kickstart back and kick all the way through. When I got it running last time, I just had to gently kick the kickstarter and the engine smoothly began to purr. Now I do the same and about 2/3 of the way through on kicking it, BAM like the kickstarter was firing out a shotgun and about breaks my foot.

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I could see kickback happening from incorrect starting procedure - usually when I use the decomp lever I sort of ignore when it pops out and rotate through until I get a lot of resistance. Then bring the kickstart to the top and put my entire body weight into a hard, smooth kick all the way through.

Personally if I had doubts about the timing I would just remove the cover and check it. It's not that tricky, and you could get a look at your cam chain and condition of the cams/valves while you're in there.

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