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1974 DT360

23 Jun 2019 18:30
480volts
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1974 DT360 #1
I purchased a 74 DT 360. Starts a 2 or 3rd kick ever time. It runs fine until it warms up. It starts to rev up and down on its own once warmed up and hot. I was told it’s sucking in air some ware. The rubber intake looks ok. A local mechanic said the block or heads may be warped. Does any one have an idea what’s going on?

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23 Jun 2019 18:39
darinm
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1974 DT360 #2
Crank seals are a likely culprit. You can try spraying some starter fluid on suspect areas while it is running and if the rpm picks up, that's your leak.

1972 Yamaha CT2 175
1972 Yamaha RT2 360
1972 Suzuki TS 185 Sierra
2001 BMW F650GS

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23 Jun 2019 19:21
DEET
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1974 DT360 #3
If the local "mechanic" didn't mention the crank seals, you might want to look for another shop...

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Where the Yamaha Enduro is still a current model...
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23 Jun 2019 21:08
asco
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1974 DT360 #4

DEET wrote: If the local "mechanic" didn't mention the crank seals, you might want to look for another shop...


Very True

You need a better source of information ..

Basic 2 stroke 101

Bike rpm climbs on it's own. - crank shaft seals are known !

abc

YAMA-LAND
818-521-2109
This email address is being protected from spambots. You need JavaScript enabled to view it. 1971 125cc AT1-C (DOROTHEA) 1971 175cc CT1-C (BRANDY) 1970 250cc DT1-C (MONICA) 1973 100cc Hodaka Combat Rat (ABBY NORMAL) 1975 DT400 (BONNIE BELL)

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23 Jun 2019 21:28
MarkT
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1974 DT360 #5
It would be extremely rare for your model that a "warped head or block" would be the source of an air leak causing the symptoms you're describing.

I'm a fan of pressure testing at 5 psi (and then vacuum testing) to find leaks and fix them. Anything else is just "guessing".

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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24 Jun 2019 03:25
480volts
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1974 DT360 #6
Thanks for the info. I rode a bike like this when I was a kid and new nothing about engines. Now that I am near 50 I am getting back into it and learning more about the mechanics. My plan is to fix everything my self. So I might be asking more questions. Is it a big deal real sealing the crank case? What sealer should I use?

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24 Jun 2019 03:42 24 Jun 2019 03:45 by RT325.
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1974 DT360 #7
Block or head sounds like car talk, well it would be down here. But check the base gasket for a sucked in flap of of gasket & he could be right!!. won't be head gasket or it'd be chuffing away & blowing compression out there but not the symptoms for your problem. Crank seals ok, but unusual to have revs rise & fall--so i don't know. Is choke on & you've wound the idle speed screw in to compensate the choke drowning effect. But to reverse that thought--is the choke jet down in the bowl cavity blocked--small fixed jet--& then running the choke only opens the airway but doesn't add fuel so make the revs rise. Yep that's it--you'll be back & tell me it is--or it's not lol. Look there before the drama of crank seals. Firstly though make sure choke is closed for normal running even before checking to see if its blocked as once closed & motor warm then choke plays no part. Set idle mixture at about 1.5 turns out, then back off the idle speed so the slide hits the bottom. Then wind the slide up say one turn for a start, that's one turn from when it starts to lift. Then start it & if you choke it make sure its flicked off & that the plastic seal in the choke shaft hasn't popped of its groove & is holding choke off from fully closing. That'll do for now--i need a coffee.

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24 Jun 2019 09:06
run103
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1974 DT360 #8
Is the oil injection connected and working
Doug

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