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Makotosun

1969 AT1 MX woods racer build

  • Yojimbo
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Replied by Yojimbo on topic 1969 AT1 MX woods racer build

I found a what is reported to be a 175 Mx jug with reed cage and carb on eBay for $120 shipped, it was delivered Saturday, gonna bring it to my guy Tuesday so he can evaluate it. Then what was described as a 175 Mx head showed up on eBay for $50 yesterday, I bought it also. Is there a difference between the standard an MX head besides the fins being cut? 

After being on the lookout for a while, seems like I did good if they are what they say they are.
Last edit: 15 Oct 2023 07:11 by Yojimbo.
15 Oct 2023 07:10 #21

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  • MarkT
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Replied by MarkT on topic 1969 AT1 MX woods racer build

Exhaust port is raised significantly on MX175 so combustion chamber in head is smaller to compensate for the loss of compression due to port closing later.
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
15 Oct 2023 07:28 #22

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Replied by Yojimbo on topic 1969 AT1 MX woods racer build

Thanks Mark, I’ll wait till I get the head to post pictures of both so maybe someone can identify them.

Thanks for reading
Jamie Galvin
15 Oct 2023 11:57 #23

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Replied by RT325 on topic 1969 AT1 MX woods racer build

47 useful videos down the side from this guy so thought i'd link it before i lose it.
I guess the video will come up which wasn't my intension.
Just not sure what i'm doing haha.
www.youtube.com/playlist?list=PLQyl8BUTh...Tc1b-Rj1S9V9Ej3qC94G
The following user(s) Liked this Post: Sneezles61
15 Oct 2023 16:06 #24

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Replied by Schu on topic 1969 AT1 MX woods racer build

Wow. Thanks for that link! Good as gold for someone like me who has never done most of that stuff.
Schu

CT1B, CT1C, JT1, JT2, DT360A, GT80B, DT100B, DT125B,
DT175B, DT175C, DT250B, DT400B, Z50, SCR950

Someday, you'll own some Yamahas
16 Oct 2023 14:51 #25

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Replied by Yojimbo on topic 1969 AT1 MX woods racer build

I’ve been watching that YouTube channel. I’ve learned a lot from him. 

I found the cylinder port dimensions in the tech section. The ports on the cylinder I just got from eBay are much smaller than the 175mx ports as described by the manual. Im pretty sure it’s a standard 175 cylinder. Let’s see if the head I ordered that was listed as an MX head actually is. I’ll report back.

Thanks for reading.
Jamie Galvin
16 Oct 2023 19:29 #26

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Replied by DaveinSC on topic 1969 AT1 MX woods racer build

The easiest way to tell the 74 Mx top end is the numbers cast into the cylinder and head, I think they were 45500? Another way is to count the fins. The 74 MX has 11 fins on the head and 6 on the jug where the 72-3 reed valve CT has 314 casting numbers and 14 fins on the head and 8 fins on the cylinder, I don’t see any casting numbers on the CT cylinder I’m looking at right now. Here’s the 175 Mx top end on my 73 ATMX
The following user(s) Liked this Post: Rick C., Gr8uncleal, Ht1kid, Sneezles61
Last edit: 17 Oct 2023 10:31 by DaveinSC. Reason: Add video
17 Oct 2023 10:12 #27

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Replied by Wrench66 on topic 1969 AT1 MX woods racer build

So you have a later reed cylinder with a piston port head :)
Nothing makes me smile like the smell of Blendzall green label ;)
17 Oct 2023 19:01 #28

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Replied by Capt.Dave on topic 1969 AT1 MX woods racer build

I use a 74 MX175 top end with a CT1 webco head pvl ignition and a 30mm short barrel Mikuni. Plenty of wins.
 
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19 Oct 2023 12:54 #29

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