Well, I bought my 9 yr old son a really low-time Bomb DS50 and we ran it for a month without a hitch. We had it out last weekend and it was running normally, then it lost all top-end power and seemed to be limited on RPM to the lower range.

I have since removed/inspected the reed valve, air cleaner, fuel and oil-inj. filters, inspected wiring on it. I removed the carb float bowl and looked for sediment. None present. This ATV has been ridden very lightly. After I put everything back together, it ran 'normally' again, but seems to cut out at the top end. (forgot to mention I removed the thumb-throttle set screw for full throttle).

The ATV still cuts out somewhat at the full throttle position, and occasionally reverts back to the low-power antics. Since I'm not a two-stroke expert, I'm baffled. Any chance it's something in the actual CVT setup rather than an engine issue? I'd like to increase the speed on this quad if possible, as well. ANY help is appreciated, and I just ordered a SVC manual off Ebay hoping it will answer a few questions. Thanks Guys!!!

[img]i/expressions/face-icon-small-confused.gif[/img]

 

I'd say it may be dirt in the mainjet of the carb. Thats very common with the miniquads. That little bike can be made to really fly with minor cheap mods and extremely fast with more $.

 

I'm all for cheap mods and going faster. I can do any of it myself with the right combo of parts. Any advise or direction is greatly appreciated.

Thanks for the mainjet suggestion- I will check into it when I'm pulling the washer out of the air intake this week.

 

OK. Here's the problem: Not being a two-stoke engine dude, I automatically figured the issue was with the INTAKE (carb), linkage, or governor. I was WAY OFF!!!

It was simply the spark arrestor screen clogged to approx. 95% +. I was looking at the wrong end of the bike. Of course, it runs great now that I pitched it in the trash! We ride on the sand, anyway.

Well, now I have developed an intimate knowledge of the little bike's entire intake system...Time to make it faster! ANY input on what to do is greatly appreciated!

Live and learn. [img]i/expressions/face-icon-small-happy.gif[/img]

 

just recieved a 2003 DS50 as a gift for my two sons from Grandpa. He bought it at an auction for around $400.
Takes a while to start it. starts and dies a lot until it warms up.
Doesn't seem to have a whole lot of power from take off. Really dogish. Even with my 9yr old on it and he doesn't weigh much.
I was wondering where you got your service manual and how much it cost?
You had mentioned ebay. You had also mentioned that removing a spark arrestor screen had solved your problem. Is that the metal screen where the air filter is?

 

The spark arrestor is in the tail pipe and sometimes they become clogged and choke the engine.

 

Thanks for your response oldyeller. Can the arrestor be cleaned? Is it safe to just remove it?

 

Yes just remove it and see if it is the problem..

 

ok, pulled it out and it was almost completely clogged. Just took it out to test ride it (good thing I live in the country). WOW. What a difference. Its like a completely different bike. Idles a lot higher now though. Looks like there is a throttle screw on the carb. Should I adjust that to bring down the idle? There is an air adjust screw as well. Do you adjust that like you would on a car carb (wait till warmed up then turn in till RPMs start to drop then back out 1/4 turn)?
It was missing the throttle limiter screw when we got it. I think I will get one and put it back in. My boys just started to ride and with this new power I think I need to break them in slowly.

How does the arrestor get clogged? too much oil mixture? someone told me I should empty the oil tank and just run mixed gas instead. They said to get the really good quality oil from a cycle shop and mix it with premium gas. What do you think?

It is still a little hard to start when cold also. How can I tell if the automatic choke is working? The other day I removed the air intake tube and put my thumb over the carb intake to manually choke it and it started right up. It did seem to start better after the arrestor was removed but still had to start it about four times before it would stay running.

Thanks for all your advice Oldyeller!

 

I think the arrestor gets clogged by leftover oil in the exhaust and certain style arrestors seem worse than others for this..Also if the engine is working hard so the exhaust is flowing strong and the pipe is very hot it will be less likely to buildup...Some poor mini's idle around all there life with the throttle screw turned in and can never blow the crap out of the pipe...It's a good excuse for dad to take it for a clean out rip every know and then[img]i/expressions/face-icon-small-wink.gif[/img]..The oil injection units tend to vary quite a bit on these machines..Yours may be too rich so running pre mix may help..You can loop the oil injection lines together if you want to try running premix.That way the pump will still get lubricated and you can easily reattach the line to the carb if you want to hook the oil injection back up....I agree a good quality oil is a must..We ran Motul 600 synthetic in our Eton with the injection system and it never fouled a plug or gave us any grief..I immediately noticed it started better once we made the switch...The oil is expensive but they don't burn very much either so it lasts a long time...As for the carb I would try just resetting your idle speed for now...If its got a bog or stumble you may have to tweak the air mixture screw a little to cure it...Also make sure you are running the correct spark plug..The electric chokes seem to cause a lot of problems on the mini's.They either don't come on or don't turn off.I don't know how to cure that other than just switching to a manual choke if its a real problem..There used to be a conversion on the Eton site that may work for others as well...Let us know how its working for you.