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78 DT175 Heat seize


flyday58
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So. After I got it all back together and rideable, I did just that. It took awhile, but my temps eventually climbed into the 200s again. Not happy. At all. So I limped home at 30 mph to keep the temp down.

But she is MUCH peppier. Very responsive to throttle inputs, noticeably better than before. So I am convinced the inside crankcase seal was bad, drawing in air and oil and causing an over-lean condition. Paul, your temps sometimes run in the 200s and you say you've gotten comfortable with that, so I am willing to allow that this may be normal of a single cylinder air-cooled behemoth like the DT175. My air-cooled twin CS5 runs much cooler, normally not over 160, and I will attribute this to dividing up the work between essentially two motors.

So I decided to fiddle with the jetting again. I took the 160 out and went back to a 140, leaving the needle jet clip where it was, one rich. Went out in the boonies, and what a bowser! Unless I cranked on the throttle, she just popped and spit and acted like her mouth was full and she was choking. So I stopped on the trail, removed the slide and put the needle one notch to the lean side.

VOILA! This is the bike I remember lusting after. Fabulous throttle response, God it was so much fun out there!!

I am going to continue tinkering with the jetting. As far as seizing and the heat, I really have to wonder if all my troubles aren't down to just not letting the old gal get completely broken in from the bore job. It's less than 300 miles since, so for now I will be showing her brush pan the dirt and grass behind my house with lots of varying throttle and just have fun for awhile. Maybe not the best way to treat an aging enduro but it's too damn much fun. Cheers all. :buzz:

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:thumb: Fabulous! That's gotta feel good.
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nice one flyday, in the crank pic..

.wheres the 'O' ring?

Why does the taper look so manky?

is there some broken material in the keyway?

Paul, the o-ring is there, just hard to see (no flash). Yes, the taper is manky but only on the surface, it doesn't extend into the metal. The original crank, however, was largely compromised where the crank seal rides so I changed it with my spare. Everything was well-cleaned - didn't take before and afters of all the ugly stuff.

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Congrats! Glad to see you got it sorted out after all the headaches. And you've set the quality DT bike pron bar quite high in the process! Have fun breaking it in.

:yeah: thanks, all!

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Great stuff Richard, let us know how she runs and in particular the temperature.

I have an inkling that mine needs a new crank seal (magneto side) an she's 'hanging' at idle briefly before settling and kangarooing on the over-run, It will be interesting to see if replacing it reduces the running temperature any

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Sure thing, Paul. Been just thrashing it around the yard yesterday but today I will venture over to the dirt pit behind our property to wind it out. We are in the county with lots of open land all round. Just have to watch for hunters with their assault rifles looking for deer to blast. :finger:

I like the max temp feature on these Trail Tech meters, saves having to stop during the ride. No, I haven't mounted mine permanently yet as I have been switching between the DT and the CS, so I can't view it while riding. But I do have a 2nd one on the way so each will have one. BTW, did you make your bracket? Looks laser-cut and all.

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Sure thing, Paul. Been just thrashing it around the yard yesterday but today I will venture over to the dirt pit behind our property to wind it out. We are in the county with lots of open land all round. Just have to watch for hunters with their assault rifles looking for deer to blast. :finger:

I like the max temp feature on these Trail Tech meters, saves having to stop during the ride. No, I haven't mounted mine permanently yet as I have been switching between the DT and the CS, so I can't view it while riding. But I do have a 2nd one on the way so each will have one. BTW, did you make your bracket? Looks laser-cut and all.

Yes mate I made it from a piece of polished stainless cut from an old broken tea urn that i binned at work..not laser cut but thanks for the comment :D

I will post up something interesting about ethanol petrol next

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Yes mate I made it from a piece of polished stainless cut from an old broken tea urn that i binned at work..
Hmm...think I'll see if I can 'procure' one of those from my hotel room next month in London. I'm sure they won't notice a kettle hanging from my travel bag!
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