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'74 TY250 carb question- anyone using these?

  • nhsteve
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I am in the middle of reviving a '74 TY250. The carb was/is in pretty sad shape. The slide had been forced down the carb bore without being aligned properly and it was bear to remove. Main nozzle (aka needle valve) and needle seriously worn by appearances. Unless it was by design I have never seen a needle that 'necks down' in the middle like this one. So for proper running it would be needing a good slide, needle and valve, plus maybe both jets and float valve. All of which I am pretty sure I can obtain, but at a cost of roughly $150+.

I have been able to start the bike (it is in surprisingly good overall condition despite the carb issue) and it rides fine in the yard. The lights even work.

My question is: Has anyone on the forum used these OKO carb kits?


At $110 plus shipping it could solve several of my carb problems. I am reluctant only because I am not at all sure that I can still use the original throttle cable. The OEM cable has a 8mm threaded ferrule that threads into the carb body top. It appears maybe the OKO does not(?). The cables are stupid-expensive for OEM, and the Venhill kits they sell eliminate the oil pump, which I was planning on keeping.

Would appreciate any input. Also, are there any other dedicated trials website? There doesn't seem to be much TY activity here.

Thanks!
13 Jun 2020 07:51 #1

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  • JayB
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I have an OKO carb on one of my Bultaco Sherpa T's and it works great!

Try www.mid-atlantictrials.com/ for some TY action and more info on the OKO carbs at www.mid-atlantictrials.com/Sales.html. Call Roger, at 410-635-6722 or email him at This email address is being protected from spambots. You need JavaScript enabled to view it.. Or try his cell phone at 443-821-6154. Besides your cable question he will also answer any questions about tuning, mounting, clearance, etc. Ask him how many TY250s he has set up. He is mostly into vintage trials but has also put the OKOs on other machines.
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13 Jun 2020 08:29 #2

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Replied by Makotosun on topic '74 TY250 carb question- anyone using these?

A great source for trials parts is in the UK: www.tytrials.com/

I’ve sourced a number of items and they are a great vendor.

This is another great TY info site, and it appears they have added a forum since was last there:

yamahaty.com/english/internat.html

Of you get one of those carbs, please post up your results, as they may be useful on a DT as well!
IF it isn't one thing, it's another.
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13 Jun 2020 12:51 #3

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Replied by Makotosun on topic '74 TY250 carb question- anyone using these?

Really funny your timing on this. I just got a text from a buddy of mine who is putting an OKO carb on his TY. He went with the Venhill cables, and a custom air box. I’ll try to post up some pics later. Also, you might see if DEET could build you some cables using your old hardware and match it to the new carb.
IF it isn't one thing, it's another.
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13 Jun 2020 12:58 #4

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Replied by Makotosun on topic '74 TY250 carb question- anyone using these?

A few pics of his air box setup:



IF it isn't one thing, it's another.
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13 Jun 2020 13:05 #5

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Replied by Makotosun on topic '74 TY250 carb question- anyone using these?

And the filter itself:









IF it isn't one thing, it's another.
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13 Jun 2020 13:06 #6

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  • JayB
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A picture of my Sherpa T 350 with an OKO carb mounted. I starts easily and runs very well.

Last edit: 13 Jun 2020 20:19 by JayB. Reason: To correct an upside down picture.
13 Jun 2020 20:16 #7

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  • nhsteve
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Replied by nhsteve on topic '74 TY250 carb question- anyone using these?

Thank you both, Jay and Makoto. Yes, I think I will probably go with the OKO setup. In the writeup it indicates maybe a bit better throttle control (but when you are as ham-fisted as I am
??).

Interesting airbox. I like it I think. I had a '76 Bultaco Matador that had a similar airbox/filter arrangement in that it consisted of a good-sized piece of flat foam over a mesh support, into the sizable airbox itself. Kind of a filter before a 'still-air' box arrangement. Wonder if your friend felt the stock setup was stifling the flow?

Appreciate the website info also, I will check them out. :Buds
15 Jun 2020 08:15 #8

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I ride vintage trials. I replaced the stock Amal on my Sherpa T with a Mikuni VM26, but this was before the Oko carbs came out. I have a couple friends who run Oko carbs. Interestingly enough they are based on a Keihin carb design. In fact if you look inside the carb you’ll see the Keihin logo cast in the carb body.
18 Jun 2020 22:20 #9

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  • nhsteve
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Replied by nhsteve on topic '74 TY250 carb question- anyone using these?

So as a follow-up, I did go ahead and purchase one of the OKO carbs from Atlantic Trials. It came really fast, within a couple of days. There were a couple of pages of what looked like potentially very helpful info, should I get into trouble with it, plus contact info.

But the enduro (or trials, in this case) gods were smiling down on me Yay2

My main concern was whether or not the threaded end of my Yamaha cable would thread into the carb top, and it does (after removal of the adjuster sent with the carb). This can be seen in one of the pics. Fit right into the rubber manifold without issues. With a new bit of gas line and some fresh non-ethanol hi-test, I rolled it outside.

One pulls the choke knob straight up, and it clicks into a full choke position (I suspect it is an enriching circuit actually). Two kicks later and the bike is started and sounds fine (I had already done the timing). A minute or two on choke and I drop it off, and blip the throttle a bit, and it settled down into a nice, low idle. It may almost be too low, but I think I have heard that some riders like this so they can have the bike in gear and running at really low throttle settings for more control. Don't know at all, as it is my first trials bike.

So, I am happy I did this. I was looking at spending almost the same money for 3 new OEM carb pieces, and my existing carb was pretty beat up, and the choke lever had an issue as well. Money well spent, and so far good service, IMHO.

Thanks for the encouragement to go this way guys.:Buds
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02 Jul 2020 13:24 #10

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