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Plug Dry

  • Gem80DT175
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Plug Dry was created by Gem80DT175

So, I've slowly been plugging away fixing up a red 78 DT175.  So excited about finally getting this thing going.  I've rebuilt the top end, changed out the bent shift shaft, along with dealing with a bunch of stripped out and sheared bolts.  Anyway, finally had it all together, put fresh oil in, bled the autolube, fresh gas - and the moment of truth!! Nothing.  Not a pop.  So, I checked for spark - had a new plug in.  Yup, definitely spark, but maybe not quite as bright and blue as it should be. BUT, it was bone dry. Kicked it over about 100 more times thinking maybe the gas/oil just needed to work its way thru, nothing.  Checked plug again.  Dry.  So now I have the carb out (I did check it before putting it back in initially and it appeared clean - main jet=clear, pilot jet= clear.). I took it ALL apart again per repair manual and everything appears clean and clear.  I checked the reed valve assembly and that too has no apparent issues/defects.  Definitely had gas in the carb when I pulled it out.  Should I soak the whole carb and parts in a carb clean kit? Any other reason no gas is getting in? Timing or something?  I don't think this has to do with gas/oil getting to the cylinder, but does the DT need a charged battery to run?  Thanks for your help!!!!
12 Aug 2022 15:10 #1

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Replied by Pedalcrazy on topic Plug Dry

Whenever I rebuild a motor and the whole system is clean and freshly installed I take an eye dropper with 2 stroke gas in it and wet the plug and squirt the remaining in the spark plug hole and then install the plug. My last build, 78DT400E, started on first kick from complete rebuild. Adding that shot of gas gives it a head start on pulling in fuel from a fresh, dry system.
1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
1968 DT1 (Project)
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Last edit: 12 Aug 2022 15:30 by Pedalcrazy.
12 Aug 2022 15:29 #2

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Replied by MarkT on topic Plug Dry

Might be the starter jet in bottom of float bowl.  I've had that damn thing cause no start on a few of my DT175's.  Older models don't seem as sensitive.  I think the newer ones were just so much leaner for emissions that they just don't start cold if starter jet plugged.

 
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 Aug 2022 20:38 #3

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  • RT325
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Replied by RT325 on topic Plug Dry

Crank seals in place. Need to be popped out to not suck at all. Get someone to kick it over while your hand seals of the carb mouth. Should be noticably sucking on an open throttle. By that time plug should be wet or she's start. Any spark is good spark & cdi spark never looks very exciting but wouldn't want a belt off it. If it fires remove hand & few more kicks on throttle.
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13 Aug 2022 20:15 #4

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  • Gem80DT175
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Replied by Gem80DT175 on topic Plug Dry

So I checked the starter jet and that was all clear.  I re-checked pilot and main and those were clear.  I pulled the choke knob out and sprayed cleaner in there - it sprayed right thru. I sprayed carb cleaner in every orifice, nook and cranny.  I set the air screw at 1 1/4 turn.  I then took Pedalcrazy's advice and thru a shot of premix in the plug hole and it fired!  Idled GREAT! But now the issue is there is no throttle response??  

It is idling with the littlest bit of throttle, but when I rev, it sounds like the video - just boggy.

So, I rechecked the assembly of the throttle valve/need jet as per the manual.  I have 2 different carbs - one from a 78DT175  and one from an 80DT175.  When I look online at year specific carb diagrams, the 80DT reflects the item numbers 42-49 which is what I am using for the upper part of the carb. I am using the lower body of the 78DT carb, as I am missing item #8 cable stopper on the 78 carb.  I can't seem to find an OEM replacement either.  I'm guessing the issue is using the upper throttle valve assembly of the 80DT to the lower part of the 78DT carb?  I would think that incompatibility would be reflected in the manual carb diagram tho, as in 2 separate diagrams I don't know. Also, when the bike is off, and I twist the throttle, I do hear the throttle value moving in there...

Things I've done:
 - new air filter with pj1 air filter oil
 - removed muffler insert - it is pretty clogged up, but when I started it up without insert, there was no change to throttle response.  
 - verified the float height at 0.83in
 - verified clip position is at 3 on jet needle
 - verified main jet is 140
 - pilot jet is 22.5
 - visually all the intake boots are good and not cracked up

I did notice a tiny leak on the float bowl, so I'm waiting for the new gasket but it doesn't seem like that slight leak would effect the throttle response so badly??

Anything else I should do or check???

This is my first time doing anything of this sort so I thank you all for your experienced input!!

 
Last edit: 14 Aug 2022 16:34 by Gem80DT175.
14 Aug 2022 14:34 #5

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Replied by Gem80DT175 on topic Plug Dry

Carb diagram
14 Aug 2022 14:35 #6

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Replied by Gem80DT175 on topic Plug Dry

14 Aug 2022 14:40 #7

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Replied by MarkT on topic Plug Dry

Are you using the slide needle from the 78 carb? 

I'm not even sure you could get that to work as the 1980 carb is really different from a 1978. 
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
14 Aug 2022 18:11 #8

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  • Gem80DT175
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Replied by Gem80DT175 on topic Plug Dry

I was as I am missing the cable stopper, but I've since found a replacement and ordered. Hopefully that will fix the throttle problem.
14 Aug 2022 20:07 #9

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Replied by MarkT on topic Plug Dry

Your video link doesn't work for me.  :(

Here's a "no rev" caused by a bad CDI in case that's what yours is doing.

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
14 Aug 2022 20:19 #10

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