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drz125 no power

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Hey guys. I am new to off road bikes. I recently purchased a 2003 drz125 for me and my 15 y/o brother for cheap. The bike starts right up and idles fine, but has no power at all. I had just rebuilt the carb and had it tuned. The bike will literally go only 10 mph at most in all gears. I know the carb is clean and the bike doesn't burn oil, but do you think it could still be bad rings? I can tell the top end has been off before but I have no idea what was done. I did search but I didn't see any threads with my specific problem. What are some causes of low compression on these motors as well?

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That's a new one. Have you checked that when you open the throttle, it is indeed opening the slide the whole way?

Don't go tearing apart the motor just yet, doing so would be a waste of time and money. You may need to, but exploratory surgery is usually a last resort.

How does the bike rev? Does the exhaust sound normal? What kind of exhaust is on it? If it's the stock one, get some allen head wrenches and pop open the can, make sure there isn't a rodent or insect nest inside it.

Is the air box on? Is the air filter clean? If not, clean it/connect the air box.

How far in do you need to pull the clutch to disengage the motor from the transmission?

Tell us everything you know about the bike and if you can, include pictures.

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That's a new one. Have you checked that when you open the throttle, it is indeed opening the slide the whole way?

Don't go tearing apart the motor just yet, doing so would be a waste of time and money. You may need to, but exploratory surgery is usually a last resort.

How does the bike rev? Does the exhaust sound normal? What kind of exhaust is on it? If it's the stock one, get some allen head wrenches and pop open the can, make sure there isn't a rodent or insect nest inside it.

Is the air box on? Is the air filter clean? If not, clean it/connect the air box.

How far in do you need to pull the clutch to disengage the motor from the transmission?

Tell us everything you know about the bike and if you can, include pictures.

Yeah the slide opens all the way. My mechanic buddy helped me with the carb and carb tuning.

The bike does still have the stock exhaust. Revs and sounds fine when sitting with no load. When adding load i.e. riding it is just won't go. I will pull the end cap next weekend since I am leaving for Singapore tomorrow morning and need to get stuff together tonight.

The air filter is clean and I have tried running it without the filter same results.

The clutch doesn't seem to be an issue, but could be. I know what clutch slipage is from my race bikes(sport bikes).

I am leaning toward low compression from the valves since it is not burning oil. They were super loose my buddy said. They were making a very loud clanking noise. Could it possibly be a burnt valve?

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DR(z) motors are talkative. I wouldn't be surprised if your friend may have made them too tight. Did he do it by ear or with feeler gauges?

Definitely do a compression test, but don't do a tear down until you've confirmed the valve lash is correct with gauges.

Good luck on your trip.

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DR(z) motors are talkative. I wouldn't be surprised if your friend may have made them too tight. Did he do it by ear or with feeler gauges?

Definitely do a compression test, but don't do a tear down until you've confirmed the valve lash is correct with gauges.

Good luck on your trip.

We haven't adjusted the valve tappets yet. He pulled the tappet covers and noticed how much play there was in them. I will check the compression soon. Do you think it could be a burnt valve causing low compression since there is no oil being burnt? I will double check the valve clearance and do a compression check next weekend though.

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Out of spec valves will cause low compression and it's a lot cheaper to fix too.

Spec is 0.003-0.005" or 0.08-0.13mm in/ex.

Yes, a burned valve will cause lousy compression. Poor compression will usually result in poor running characteristics. I haven't gotten around to my fixing my street bike, but it has ZERO compression on one cylinder. I emphasize zero because it reads zero. Although with nearly 40K on the clock, it's time to look over her insides anyway.

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And make a motor loud...without doing real damage if you get lucky....I have been off by a tooth before...no damage, but the motor runs like crap.

Tom

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Thanks for the help so far guys...I am in Singapore right now and will look at it next week. I definitely check the timing. Hopefully it is not too far off.

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Ok guys I had a buddy look at the compression of the bike while I am in Singapore. He said it was only around 75. He said he adjusted the valves to within spec and now has a compression of 145. I would assume 145 is acceptable. When I get back in a few days I will let you know if it solved the problem with the bike having no power.

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145 is fine. I'm amazed it ran on 75 PSI. Well, not amazed, those DR-Z motors are pretty tolerant, but I didn't think that tolerant.

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Well the bike ran fine for about 30 minutes the other day when I picked it up. I am surprised how little power these 125s have.

The kicker is that the bike lost all compression the same day. I pulled the valve cover and noticed that the previous owner didn't tighten the cam gear onto the cam shaft and the bolts backed themselves out and the gear came off the cam. I am in the process of getting a leak down gauge to see if the it bent a valve which it probably did. Need to check the timing now too.

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Sounds like the bike was sick from the start. They are not powerhouses, but should be able to scoot you around just fine.

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That's a bummer, but at least these motors are fairly easy to work on. The only special tool you'll need for the top end is a valve spring compressor. An automotive one will work (if you need it), but it'll be too big, take up the slack with some washers or a large nut.

Good luck.

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Well guys I put the cam gear back on the cam and set the timing last night. I went to start it and it fired up and ran fine. I am still going to do a compression check to make sure. I am borrowing a friends gauge because I think mine is broke because it only reads about 75 psi, but the bike is running strong. Well strong for a 125 4-stroke. If the compression is indeed decent I need to take it out riding for awhile because this is a present for my little brother's birthday and I don't want it the motor to go on him. I will keep you posted.

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Well the motor has 152 psi of compression. Looks like I need to spring for a new compression gauge. The compression with two different gauges of last night and they both read around 150 psi (stone cold).

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Sounds like you're good to go. If you had a bent valve, I really doubt you'd see compression above 50 PSI, let alone 100.

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Instead of starting a new thread. Where do you guys get a petcock rebuild kit or a new petcock for the drz? I see new petcocks on ebay for $70 but that seems to be too pricey. The problem with my petcock is that it will not stop the flow of fuel at all. It slows it a small amount bu that is it.

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The rubber in the petcock dries out. When you turn it on or off it tears. There really is no fix and no rebuild kit. Usually I have found entire tanks with petcocks on ebay for 40 bucks. A cheap fix is to install a inline petcock below the factory one. Should be less than a $10 fix

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