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Makotosun

Anybody drilled the boyesen port holes on a 1972 DT 250?

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Anybody drilled the boyesen port holes on a 1972 DT 250? was created by Hooka-2

Anybody done the mod to drill the boyesen ports on a 72 or 73 DT 250? what were your results? better, worse, no difference? I was thinking about doing it along with cleaning up the ports (matching and widening the exhaust port) any input would be appreciated. Also trying to get a hold of Dave Meis to do the sleeper pipe. Riding MX bikes all these years I didn't realize how gutless these DTs were in stock form until I bought one. Love the looks but needs some balls
21 Oct 2021 15:20 #1

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Replied by RT325 on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

I guess you like modifying yourself to feel the results of your work & sure nothing wrong with that!!. If i had a DT2--instead of DT1--i'd like to try a DT2MX top end & make a suitable pipe. I had a DT2MX new & they fair turned on--on the track. Probably a bit wild for the street but the right pipe to spread the power more would help.
22 Oct 2021 04:21 #2

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Replied by MarkT on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

Mr. Meis also does porting. 
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
22 Oct 2021 05:34 #3

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Replied by Hooka-2 on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

I do like working on things. I'm new to the DT world but I have done extensive work on old school jet skis. I know I need to do a lot more research before I really dig in . I have reached out to Meis for pipe work as I know (at least on skis) that is the largest gain in power. At this point I'm just reaching out for those with experience of different mods to see what will work on the street.
22 Oct 2021 06:28 #4

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Replied by Storbeck on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

Have you given the cylinder a good look where the boyesen ports would be? I'm not super familiar with the 250 cylinders but I think there is a good chance that there is a cylinder mounting stud in the way and no room to put a boyesen port there. 
22 Oct 2021 08:13 #5

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Replied by Hooka-2 on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

I have not removed the cylinder to inspect the area as of yet. I based my question off of a post I read that showed pictures of how someone did it on a DT175. I'm only assuming (maybe incorrectly) that it would be similar on a DT250
22 Oct 2021 09:25 #6

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Replied by Rick C. on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

Good stuff in here....

yamaha-enduros.com/index.php/other-manua...-factory-racing-tips
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22 Oct 2021 11:41 #7

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Replied by Hooka-2 on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

Thanks Rick. I saw someone had referenced this document in other threads. It was on my list of must reads
22 Oct 2021 11:56 #8

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Replied by Rick C. on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

It starts on page 6-1. ( On the book page, not the download page. )
Enjoy !
22 Oct 2021 12:52 #9

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Replied by Hooka-2 on topic Anybody drilled the boyesen port holes on a 1972 DT 250?

Looks like some good stuff. I also got a hold of Dave. I'll be sending him my pipe. Also plan on buying a couple used cylinder to experiment with
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22 Oct 2021 14:16 #10

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