Author Topic: Stuttering DT problems  (Read 546 times)

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Offline Danfr

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Stuttering DT problems
« on: April 26, 2019, 01:50:06 AM »
Hey guys!

Finally passed the exam and was granted access to this mecca of information! Pumped.

I just picked up my first DT and first two stroke two weeks back. It's a 1991 DT200R up here on Vancouver Island Canada. I decided as a weekend challenge to strip it down, repaint the frame, and rebuild; cleaning all parts as I went. The rebuild went great and everything is back together.

The bike was a bit of an issue when I picked it up and it still has the same issue. At around 6000 rpm and over quarter to half throttle, the bike starts stuttering. The carb was completely cleaned up. Pilot is 35. I have also tried 170, 180 and 190 mains all with the needle second from the top. All have the same issue. I should also add that the oil pump is not installed and running off premix. The previous owner ditched the oil pump. I just picked up a used one and the rebuild kit should be arriving today.

Also I used standard automotive 50/50 coolant and the bike doesn't appear to warm up. Is there a particular two stroke coolant? This is my first water cooled bike and two stroke. Perhaps the indicator is not connected but it does sit a one particular spot. (coolant issue could be unrelated, but I figured the more info the better).

Thanks for your help!














http://youtu.be/G8WuBgtVdTM

Offline Devondan

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Re: Stuttering DT problems
« Reply #1 on: April 26, 2019, 05:31:09 AM »
Looks like a nice job! You know that 90% of all carb problems are electrical, right?!

At a 1/4 to half throttle you are no where near the main jet. I have no idea what the standard jets are on your bike, but if you are running on premix you will have weakened the mixture by adding oil. So you may be lean on the needle. I?d ride it into the stutter zone for a bit then take the plug out and have a look, if it?s lean, lift the needle, if it?s rich drop it and see how that goes.

I?d also change the plug and cap and check all the connections and grounds are good especially on a newly painted frame.

My thoughts anyway! - I was in BC last year, lovely part of the world btw!

Dan
IT  400D - Trail riding
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Offline Danfr

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Re: Stuttering DT problems
« Reply #2 on: April 26, 2019, 05:38:37 AM »
Looks like a nice job! You know that 90% of all carb problems are electrical, right?!

At a 1/4 to half throttle you are no where near the main jet. I have no idea what the standard jets are on your bike, but if you are running on premix you will have weakened the mixture by adding oil. So you may be lean on the needle. I?d ride it into the stutter zone for a bit then take the plug out and have a look, if it?s lean, lift the needle, if it?s rich drop it and see how that goes.

I?d also change the plug and cap and check all the connections and grounds are good especially on a newly painted frame.

My thoughts anyway! - I was in BC last year, lovely part of the world btw!

Dan

Sounds great. I'll pop in a fresh plug and chop it.

I have checked all the connections. I've wired a few bikes in the past and am a electrician by trade so I know the importance of a good connection :)

I'm suspicious of the fuel being from last year and premixed by someone else. My oil pump rebuild kit is coming today. I'll get that installed first and foremost and then do the chop.

Thanks for your help!

Offline fred99999au

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Re: Stuttering DT problems
« Reply #3 on: April 26, 2019, 07:45:50 AM »
If'n your putting the oil pump back, I'd be putting the stock jets in the card so that the mixture is factory.

Offline Danfr

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Re: Stuttering DT problems
« Reply #4 on: April 26, 2019, 08:01:23 AM »
If'n your putting the oil pump back, I'd be putting the stock jets in the card so that the mixture is factory.

Great tip! Isn't the stock jetting 180 main and 35 pilot for a 1991 DT200r? I don't have the manual

Offline Danfr

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Re: Stuttering DT problems
« Reply #5 on: April 26, 2019, 09:05:19 AM »
The oil pump rebuild has come in and I have mounted the oil pump. Where does the oil feed into the carbie? Cheers

Offline enduras_wr200

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Re: Stuttering DT problems
« Reply #6 on: April 26, 2019, 10:49:17 AM »
   Hi there mate, I think that on the DT200R the oil feeds into the rubber intake. It should have a brass nozzle on the right side of it. It can't be seen on your picture as its from the left side. 1989 models (and I don't know if there has ever been a change in jetting throughout the years) is 150 main jet, 25 pilot jet. If all the work took place in a weekend's time, congrats!



   Cheers, Fanis

Click here to get the DT200R supplement manual: http://www.dropbox.com/s/117odk5zegjv5y5/DT200%20Supp.zip?dl=0

Offline Danfr

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Re: Stuttering DT problems
« Reply #7 on: April 26, 2019, 12:39:05 PM »
   Hi there mate, I think that on the DT200R the oil feeds into the rubber intake. It should have a brass nozzle on the right side of it. It can't be seen on your picture as its from the left side. 1989 models (and I don't know if there has ever been a change in jetting throughout the years) is 150 main jet, 25 pilot jet. If all the work took place in a weekend's time, congrats!



   Cheers, Fanis

Click here to get the DT200R supplement manual: http://www.dropbox.com/s/117odk5zegjv5y5/DT200%20Supp.zip?dl=0

Thanks for the supplements! Ya it was over the weekend. 4 day weekend, granted. But it was some very long days.

Ok, so I think someone has removed the nipple that I should be attaching my oil hose to....





I was really hoping to get the bike up and running this weekend. Does this screw look correct?

Offline Danfr

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Re: Stuttering DT problems
« Reply #8 on: April 26, 2019, 01:09:40 PM »
Just found a photo of what i should have  :(



Offline enduras_wr200

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Re: Stuttering DT problems
« Reply #9 on: April 26, 2019, 01:41:41 PM »
   Oh yes, I was wrong thinking it was on the right side..it should be on the front center exactly as you posted. Do yourself a favour and ask a Yamaha dealer, the last time I bought one was no more than 28euros new. If you don't want to wait for the delivery of a part like that, I'm sure you can find a suitable nipple on sites with carb parts. Most carbs come with no oil feeding nipples on them but they are ready to receive one which can be found in the carb parts section. It most probably won't be the exact match but I bet you can get the job done!


  Cheers, Fanis