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Makotosun

1975 DT175 timing questions

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Replied by Yammiedodger on topic 1975 DT175 timing questions

Hi Again

The flywheel itself looks in pretty good shape compared to mine and most of those I've seen. If you see any play or sticking on the advancer arm its well worth unscrewing it and then taking it apart for cleaning and lightly lubing the pivot post. Be very careful when you ping the 'e' clip off as they're easily stretched and clip into a shallow groove on the post.

The mark you can see on the outside of the flywheel should line up with a thin steel projection on the end of a source coil at 1.8mm btdc (its not easy to make out as you see it end on and its around a 1mm thick).

Unless your points are way out of gap it all falls more or less into place and the timing is fully advanced after around 1800rpm, the whole advance/retard mechanism is only there to make it easier to start - that's all!
11 May 2020 00:15 #11

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Replied by GJVGC on topic 1975 DT175 timing questions

Thanks for all the information.
I definitely didn’t have that mark on the outside of the flywheel aligned with anything but the manual definitely does not mention it.

Here is a picture of the bottom of the head.


The crank seal behind the flywheel is leaking some, could the air leak be the cause? Combination of timing and air leak?
11 May 2020 04:52 #12

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Replied by RT325 on topic 1975 DT175 timing questions

Not hitting the head or you'd see it all the way around. Interesting though how the transfers have kept carbon from forming at that point & never seen that before. Or mine are never together long enough to form carbon more likely lol. Oh yeah, i see the speckled bits MarkT mentioned on top. Might pay to lift the cylinder for a look. Unlikely a knock will randomly start. Just wondering if the flywheel nut isn't tight enough & its working on the key, but wouldn't run long if that's the case, except those smaller steel flywheels aren't that heavy. Sorry if i'm doubting your tightening ability but just randomly thinking up possible causes.

Also, those advance flywheels can get clattery/rattly with the cover off but yours looks in good condition.
Last edit: 11 May 2020 05:12 by RT325.
11 May 2020 05:09 #13

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Replied by GJVGC on topic 1975 DT175 timing questions

Here a few pictures



I torqued the flywheel bolt to 42 ft lbs. is that correct? I took the flywheel to inspect it just in case anything was loose but everything looks ok. Could it be the advance mechanism in the flywheel is bad? I took it apart and cleaned it. Seems to spring back but doesn’t have the small rubber piece under the arm.
Last edit: 11 May 2020 06:40 by GJVGC.
11 May 2020 06:30 #14

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Replied by MarkT on topic 1975 DT175 timing questions

Air leak could be the problem, definitely.

I don't see any corresponding dings in the head so probably not debris which is a good thing... sometimes a bearing starts to come apart and the pieces ding up the piston/head.
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
11 May 2020 07:09 #15

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Replied by GJVGC on topic 1975 DT175 timing questions

Thank you.

Where do these engines mostly leak out of?
Left and right crank seals?
Where should I look?

I cleaned up the head and it looks fine to my eyes.
11 May 2020 07:19 #16

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Replied by GJVGC on topic 1975 DT175 timing questions



Cleaned the carbonbuild up on the piston. What do you guys think?
11 May 2020 09:42 #17

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Replied by JimA on topic 1975 DT175 timing questions

I maybe wrong but this does not look like the stock piston, mine does not have all of the numbering on it. Not that that is bad, just something to be aware of.
11 May 2020 09:56 #18

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Replied by GJVGC on topic 1975 DT175 timing questions

Thanks for sharing.
A quick google shows that part number being a .50 mm oversize piston but for a dt175 from 1978. Wiseco doesn’t list a piston for a 1975 dt175.

Are the pistons the same?


Last edit: 11 May 2020 11:38 by GJVGC.
11 May 2020 10:33 #19

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Replied by GJVGC on topic 1975 DT175 timing questions

Figured out how to load a video
Here is a video of the first time firing it up
There is not a noticeable noise


The 2nd day
Noise became much louder


The bike idles fine and starts first kick. Was driven around the neighborhood for about 10 mins total. All that was done was to set idle screw and make sure air screw is 1 3/4 turns out.
11 May 2020 16:06 #20

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