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TOPIC: 1976 DT175C Flywheel & Timing

1976 DT175C Flywheel & Timing 08 Feb 2019 16:43 #1

  • Camp3
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I want to understand how the flywheel assembly works relative to the timing advance/retard mechanism. My flywheel has no drawings on assembly out there. Parts diagrams just show the flywheel, not spacer, snapring or advance mechanism. I have read and searched about this and there is some information out there but I need to go to the forum to get more help.

Picture 1 is one I snag'd from Ebay, where it shows the flywheel and collar/spacer installed with looks like a special circlip. This is not to be had anywhere on planet earth. When I bought it, the owner mumbled something about playing with the advance to get more power...I didn't think anything of it. I guess he's the guy that lost the circlip.


Picture 2 is the collar sliding on the flywheel shaft.


Picture 3 is the collar seated on the flywheel shaft


Picture 4 is the collar off of the shaft to show the end flared and the notch. I am guessing the notch is where the advance pawl is placed when the timing procedure is being done.


More pics and my actual questions in the next post, I am out of space to add more.
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1976 DT175C Now Running!
1975 DT100B Next Up
1974 DT250A 3rd in Que
1992 FJ1200
Primary Home Long Grove, IL
Secondary Home UP of MI

1976 DT175C Flywheel & Timing 08 Feb 2019 16:54 #2

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Picture 1 is instructions on the 175 series to fix the mechanism in place and then time according to specs I think it is 1.8 Deg BTDC.


Picture 2 show the timing mech


Picture 3 shows where I think the timing cog should fit into the spacer when following the attached instruction. It doesn't say anything about where that bit should fit into the spacer.
Is this correct? and if so, the spacer on the flywheel shaft is only fixed on the with a circlip, I can spin the spacer around easily. The cam is on the spacer, so if I can spin the spacer wont that affect my timing. I suppose I have read way to much into this..but what does the forum think?


Picture 4 is my favorite steak sauce.
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1976 DT175C Now Running!
1975 DT100B Next Up
1974 DT250A 3rd in Que
1992 FJ1200
Primary Home Long Grove, IL
Secondary Home UP of MI
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1976 DT175C Flywheel & Timing 08 Feb 2019 17:10 #3

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This might work to keep the spacer seated at the proper location on the flywheel but seems made of unobtanium as well. Smalley Steel ring company wants min lot of 2500.


Picture 2 is a standard external circlip that may work if I grind the edges down.
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1976 DT175C Now Running!
1975 DT100B Next Up
1974 DT250A 3rd in Que
1992 FJ1200
Primary Home Long Grove, IL
Secondary Home UP of MI

1976 DT175C Flywheel & Timing 09 Feb 2019 09:41 #4

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The advancer arm tip that engages the cam sleeve looks like it is broken off.
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1976 DT175C Flywheel & Timing 09 Feb 2019 09:41 #5

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I hate to reply because what I have to say might be bad news... when the guy said he "modified the advance" it looks like he ground down the lever that extends into the slot on the points cam ("spacer")? Hard to tell but sure looks that way and it sounds like you can just spin the cam around wherever you want? If so, that's not right and will never work.

I have a NOS model F140 flywheel in my spare parts so here's what it should look like. Lever extends into slot.




Here's a picture of the mechanism in the "retarded" position.



Here's a picture from inside the flywheel with the lever moved to the "full advanced" position and a probe put through the holes to hold it there:






.
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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

1976 DT175C Flywheel & Timing 09 Feb 2019 09:57 #6

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The above might not be too helpful when setting the timing... so here's what it looks like from outside the flywheel. In this first photo I've inserted the probe into the area you use to pry the advance lever into the fully advance position.




In this picture, I'm prying the lever up so the holes align to the left... a second probe, thick wire, small drill bit, etc is put through those holes to keep the mechanism fully advanced when setting the timing.



Here's a close up showing where I'm prying and the lined-up holes where you need to put the second pin to hold the advance lever when timing.




Hope this helps. If your lever is not destroyed, for the snap ring, you could use anything that fits the groove... even a standard one that has the ears ground off. It's not that critical.

:Buds




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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

1976 DT175C Flywheel & Timing 09 Feb 2019 10:27 #7

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DEET wrote: The advancer arm tip that engages the cam sleeve looks like it is broken off.


I just noticed DEET responded with a perfect one sentence explanation while I was taking pictures and writing my "novel" saying the same thing... Sometimes I go into way more detail than needed. :Ugh
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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

1976 DT175C Flywheel & Timing 09 Feb 2019 10:46 #8

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If you wanted to do a cheap repair, you could eliminate the advance by rotating the points cam ("spacer") to the fully advanced position and locking it in place. Bike will run just fine, you won't notice the difference.

The key is getting the cam in the correct position before locking it in place... not difficult... just very important.

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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

1976 DT175C Flywheel & Timing 09 Feb 2019 11:44 #9

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First of all Thank You for helping me out. Now that I see what it is supposed to look like and how its supposed to operate I can envision how this works. Thanks for all the pictures and the descriptions and how to set the timing.

I guess I have some options
  1. Try to repair the advancer arm tip in some way
  2. Source a complete F140 Flywheel
  3. Find another 120 MM Flywheel & Stator maybe from a Blaster or a later DT175 that has a CDI Ignition. I will have to get the complete kit.
    I saw an earlier post about compatibility
  4. Fix it in place (thanks MarkT) which is what I will probably do, the budget overrun has been audited and she is not happy at the amount of $$ being put into this project
  5. Upgrade to the 12 volt Vape system or one like it

So I guess I will really take a hard look at#4 while I search for another flywheel with an advance mech in it...they are probably pretty rare too. Just like this "one off" 1976 DT175.
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1976 DT175C Now Running!
1975 DT100B Next Up
1974 DT250A 3rd in Que
1992 FJ1200
Primary Home Long Grove, IL
Secondary Home UP of MI

1976 DT175C Flywheel & Timing 09 Feb 2019 12:03 #10

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Blaster ignition would be a bit of a hassle to fit.

If you decide to fix the cam in place I've done it before and can post some ideas that might help.

PM sent on the flywheel.
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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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