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Choked up in low revs

11 Sep 2019 13:31
pmgDT
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Choked up in low revs #1
Hi,
I've only just started using my DT175C and on the throttle from idle to 4k revs it's choked up and as soon as it hits 4k revs it takes off like a scalded cat.
My guess is pilot jet? but maybe some other cause.

I've included a couple of links to videos of my son riding it. I've been teaching him to ride and he's coming along great.




Any help much appreciated.
Thanks, Peter

Getting older everyday

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11 Sep 2019 16:04 11 Sep 2019 16:07 by RT325.
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Choked up in low revs #2
Sounds ok from where i'm sitting but to get a better idea get your boy to pull about two gears higher accelerating from low revs. Maybe keep changing up as he goes. Maybe i'm not hearing the audio very clearly as a lot of other noise like piston rattle--maybe its just general running noise & nothing more sinister.
Just rethinking, could you do a stationary video of it idling & then bring it up slowly through the cutaway/needle/ main jet area if you're realy worried about it.
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11 Sep 2019 16:09
run103
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Choked up in low revs #3
Its a 2 stroke. that bike sounds very good to me also. Make sure the air filter is not too restrictive and have fun.
Doug
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11 Sep 2019 21:01
MarkT
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Choked up in low revs #4
Sounds pretty good to me... the only oddball thing I can think of is the advance mechanism in the flywheel might be sticking or modified by a previous owner?

Should be fully advanced not far above idle speed. You could check the advance movement with an automotive timing light.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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11 Sep 2019 21:27
RT325
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Choked up in low revs #5
Seeing i can't find anything wrong with it in the video-- can i point out the shocks should have the reservoir the the front. Well i had to pick on something didn't i --sorry. 9 out of 10 people do that, so ya not alone, & it doesn't matter.
www.partzilla.com/catalog/yamaha/motorcy...ar-shocks-chain-case
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11 Sep 2019 21:40
MarkT
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Choked up in low revs #6
I'm pretty sure the thermal flows on the 1976 DT175's do not fit with reservoir forward unless you remove the chain guard.

yamaha-enduros.com/index.php/workshop-2/...uros/105-1976-dt175c

I just checked the pictures in the owner's manual... reservoirs are to the rear...

And yes... many people do mount them backwards on models that had them mounted forward... I think you have to on 76 175 with the factory "forward mounted" shocks.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

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12 Sep 2019 02:55 12 Sep 2019 02:55 by RT325.
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Choked up in low revs #7
moto7777.wixsite.com/redneckmechanics/dt175
Ok, in desperation to prove i'm right i've proved i'm WRONG. [Apologies] Hope my wife doesn't get wind of this or i'll be Apologizing all the time. Might add i've never ever seen them mounted rearwards from new & i would've assembled those new in "76 so that's it--memory is @##$%$d. So to start again--& not related to this bike--why do people have their headlight looking for possums up in the trees. Brand new bikes in advertising pics & light turned noticeably upwards. Interesting the Partzilla link shows it forward but can see what you mean by Chainguard getting in the way as i see the shocks are forward mounted on the arm compared with earlier models Still looks wrong back ta front lol. Look at the link, lots of pics.
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12 Sep 2019 06:36
MarkT
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Choked up in low revs #8
I wouldn't say you're "wrong"... Yamaha is for making a model that the shocks need to be installed backwards to fit. :haha

I can see it now... some smart engineer probably designed the new frame in 1976 and spec'd the Thermalflows and then got a call from production saying the shocks wouldn't fit without mounting them backwards... :Ugh

:Buds

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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12 Sep 2019 08:58
pmgDT
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Choked up in low revs #9
Thanks for your input guys. Probably difficult to hear but when you're on the bike you can feel it's sluggish in the low revs before it takes off at 4k.
I've leaned the mixture out a little as the plug is showing rich. Still ironing out some little bugs but it sure is fun to ride and my son loves it.
MarkT, I haven't forgotten you found that fuel tank for me so big thanks and it's just about still holding fuel after I had to have some pinholes repaired.
Thanks again, Peter




Getting older everyday
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13 Sep 2019 05:07
RT325
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Choked up in low revs #10
As MarkT says, check the timing advance. If its got the auto advance which i can't find looking though Partzilla--if it has then good idea to pull the flywheel & give the mechanism a grease up where the cam moves on the center. Once again--if it has--then someone might've fitted a heavier spring if the old one broke, in which case it could be holding back on retard until up in the revs. All pretty unlikely. Otherwise just check the points have a good gap up to 15thou & not less than 12 without worrying too much about timing just yet as should be in the ball park.
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