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Offline kenny

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dt1 question
« on: December 04, 2017, 12:47:52 AM »
hi
i had a question about the dt1 250 from 71
i bought an dt1 from the usa but the headlight is a sealed beam one and it is broken i know back in the day you just throw it away and got youself a new one , does anyone have an idea what kind off headlight i can use to replace mine
also i bought a dt1 barrel with on the side YC 246 cc i ve been told its a barrel of a dt1mx from 71 or 72 does annyone know if this is correct ?

thanks

kenny

Offline sleepy

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Re: dt1 question
« Reply #1 on: December 04, 2017, 09:50:22 AM »
The original headlight wasn't a sealed beam, they had a removable bulb. The light was the same pretty much on all the DT/RT series. They used a 6 volt 35 watt dual filament bulb.

If the barrel is an MX it will be chrome plated inside. I have had a look at one I have here and it only has the 246 marking on it with nothing else.
Of course it has to be piston port to be a DT1. The first of the DT2's came out in 71 with the reed intake but all the engine numbers started with DT1 up until the 74 DT250.

Offline OverTheHill

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Re: dt1 question
« Reply #2 on: December 05, 2017, 06:42:55 PM »
DT1MX had a boreable cast liner cylinder [i have one] but DT1GYT kit cylinder was chrome [i recently sold one]. Assembled them new where i worked plus fixed them when they broke which was often lol. The DT1MX cylinders wore out pretty bad but the Chrome GYT Kit cylinder lasted well. I did end up with someones stuffed chrome bore that had an LA Sleeve fitted that was made out of real good stuff & lasted for ever & only recently sold that on a motor. I'll fight my way the crap & have a look at what's stamped on the side of the cylinder [DT1MX cylinder]. I'll find a pic so you can have a laugh at what it's on & not been run for years but does go & actualy fair goes like hell/ Just remembered i have a 360 crank in that one so 70x70mm whatever that works out too.

Offline sleepy

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Re: dt1 question
« Reply #3 on: December 05, 2017, 08:17:51 PM »
DT1MX had a boreable cast liner cylinder [i have one] but DT1GYT kit cylinder was chrome [i recently sold one]. Assembled them new where i worked plus fixed them when they broke which was often lol. The DT1MX cylinders wore out pretty bad but the Chrome GYT Kit cylinder lasted well. I did end up with someones stuffed chrome bore that had an LA Sleeve fitted that was made out of real good stuff & lasted for ever & only recently sold that on a motor. I'll fight my way the crap & have a look at what's stamped on the side of the cylinder [DT1MX cylinder]. I'll find a pic so you can have a laugh at what it's on & not been run for years but does go & actualy fair goes like hell/ Just remembered i have a 360 crank in that one so 70x70mm whatever that works out too.

All the ones I've seen must be the GYT kit. All the one's I've seen in the last 20 years has had the chrome bore and all are stuffed. I thought the DT1MX's were just a Dt1 with a factory fitted GYT kit but obviously not.

Offline OverTheHill

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Re: dt1 question
« Reply #4 on: December 05, 2017, 09:50:47 PM »
DT1MX had a boreable cast liner cylinder [i have one] but DT1GYT kit cylinder was chrome [i recently sold one]. Assembled them new where i worked plus fixed them when they broke which was often lol. The DT1MX cylinders wore out pretty bad but the Chrome GYT Kit cylinder lasted well. I did end up with someones stuffed chrome bore that had an LA Sleeve fitted that was made out of real good stuff & lasted for ever & only recently sold that on a motor. I'll fight my way the crap & have a look at what's stamped on the side of the cylinder [DT1MX cylinder]. I'll find a pic so you can have a laugh at what it's on & not been run for years but does go & actualy fair goes like hell/ Just remembered i have a 360 crank in that one so 70x70mm whatever that works out too.

All the ones I've seen must be the GYT kit. All the one's I've seen in the last 20 years has had the chrome bore and all are stuffed. I thought the DT1MX's were just a Dt1 with a factory fitted GYT kit but obviously not.

Yep still plenty of oversize single ring DT1MX kits on ebay. Be lucky to find a genuine kit for a chrome bore as had a ring with parallel faces as opposed to keystone tapper top face that i 'think' the DT1MX had but might be wrong on that, different thickness anyway. Chrome cylinder ring was of a different material & F$%n Dopey Me finished off a pretty worn but usable cylinder that i had for 30/40 years & thought--give it another run & had a genuine piston but no ring, so shuffled through a box of old rings & thought 'that one' do as fitted ring groove & the bore. Took about 1 minute to absolutely bugger it beyond use & pissed myself RIGHT OFF. Mate did that in the mid "60's on a square barrel villiers starmaker motor, think he got a special cylinder for it & did the same thing without realising. I thought--i'll never make that mistake lol. DT1 GYT Kit we got in late "68 for the new square S/arm DT1. Complete top end plus carb & chamber plus a "21 front wheel. DT1MX by memory would've arrived in 1970 with the round tube S/arm & ready to race out of the box--well till the gearbox gave up the next week!!. Boss got an RT1MX--same bike bigger motor. I pinched that motor for my "68 DT1 for a meeting while he was off overseas. Was a bit of fun for sure. Anyway--forgotten the question.

Offline sleepy

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Re: dt1 question
« Reply #5 on: December 06, 2017, 11:36:21 AM »
DT1MX had a boreable cast liner cylinder [i have one] but DT1GYT kit cylinder was chrome [i recently sold one]. Assembled them new where i worked plus fixed them when they broke which was often lol. The DT1MX cylinders wore out pretty bad but the Chrome GYT Kit cylinder lasted well. I did end up with someones stuffed chrome bore that had an LA Sleeve fitted that was made out of real good stuff & lasted for ever & only recently sold that on a motor. I'll fight my way the crap & have a look at what's stamped on the side of the cylinder [DT1MX cylinder]. I'll find a pic so you can have a laugh at what it's on & not been run for years but does go & actualy fair goes like hell/ Just remembered i have a 360 crank in that one so 70x70mm whatever that works out too.

All the ones I've seen must be the GYT kit. All the one's I've seen in the last 20 years has had the chrome bore and all are stuffed. I thought the DT1MX's were just a Dt1 with a factory fitted GYT kit but obviously not.

Yep still plenty of oversize single ring DT1MX kits on ebay. Be lucky to find a genuine kit for a chrome bore as had a ring with parallel faces as opposed to keystone tapper top face that i 'think' the DT1MX had but might be wrong on that, different thickness anyway. Chrome cylinder ring was of a different material & F$%n Dopey Me finished off a pretty worn but usable cylinder that i had for 30/40 years & thought--give it another run & had a genuine piston but no ring, so shuffled through a box of old rings & thought 'that one' do as fitted ring groove & the bore. Took about 1 minute to absolutely bugger it beyond use & pissed myself RIGHT OFF. Mate did that in the mid "60's on a square barrel villiers starmaker motor, think he got a special cylinder for it & did the same thing without realising. I thought--i'll never make that mistake lol. DT1 GYT Kit we got in late "68 for the new square S/arm DT1. Complete top end plus carb & chamber plus a "21 front wheel. DT1MX by memory would've arrived in 1970 with the round tube S/arm & ready to race out of the box--well till the gearbox gave up the next week!!. Boss got an RT1MX--same bike bigger motor. I pinched that motor for my "68 DT1 for a meeting while he was off overseas. Was a bit of fun for sure. Anyway--forgotten the question.

DT1 talk certainly brings back memories for me having bought a round swingarm one S/H when I was 14. It came from a guy that worked at a Yamaha shop. Had all the lights on it but they soon came off and it also came with a GYT kit which went on. Certainly went better with the kit fitted but noisy as hell with that open chamber. My plan was to start racing it with a lowered frame after reading a magazine article on converting it into a MXer. I was talked out of it by my local MX expert and shop owner and bought a 73 TM125 instead. I kept the GYT stuff and sold the bike on but after looking at the barrel some 15 years ago found the chrome coming off with corrosion under it. Have made a sleeved and fitted it and just recently sold it for use on a VMX bike.
Not much to do with his original question but you get that.

Offline kenny

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Re: dt1 question
« Reply #6 on: December 07, 2017, 02:44:07 AM »
thanks for the information guys
the cylinder i have is boreable with reed intake
on internet i cant find anything of a cylinder that starts with YC

cheers

kenny

Offline sleepy

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Re: dt1 question
« Reply #7 on: December 07, 2017, 10:44:38 AM »
thanks for the information guys
the cylinder i have is boreable with reed intake
on internet i cant find anything of a cylinder that starts with YC

cheers

kenny

Reed intake will make it a DT2/3 or possibly a DT2MX, I had a look on a DT2 barrel and can't see YC anywhere only 246cc. Can you post a picture or a link to a picture?
A lot of people have been conned into buying bikes that are listed as DT1's only to find they are DT2/3's as they all start with DT1 engine and frame number. What type of cylinder is on the bike reed or piston port?

Offline sleepy

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Re: dt1 question
« Reply #8 on: December 07, 2017, 12:43:07 PM »
Found this on Ebay.
https://www.ebay.com.au/itm/New-Yamaha-Headlight-Bulb-CT1-CT2-CT3-DT1-DT2-DT3-RT1-RT2-RT3-175-250-360-400-DT-/281985258943
It is a sealed beam probably like the one you have but there is a list of other Yamaha's that share the same size light.
I may even order one for my RT3 and keep it as a spare.

Thought I'd put up a photo of the RT3. It's had a front wheel rebuild with a new trials tyre and a new repo seat cover since the photo.


Offline OverTheHill

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Re: dt1 question
« Reply #9 on: December 07, 2017, 02:07:52 PM »
Oh hell that's suddenly opened a different can of worms. reed i "72 on so you've either bought a DT2 or DT3 cylinder if it looks the same in the way it fits on, base gasket, head gasket etc. Or it's a DT2MX cylinder which looks a bit squarer in the fining, head fins are taller too if you have the matching head. Need pics please if pos. Only problem will be--if you 'do' have a "71 piston port DT1 7 go to fit a reed cylinder then there's a conrod length difference of about 5 or 6mm. Same problem doesn't happen with a 360 going from piston port to reed. Confusing myself now so i'll leave it at that.

Offline sleepy

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Re: dt1 question
« Reply #10 on: December 07, 2017, 05:20:22 PM »
Oh hell that's suddenly opened a different can of worms. reed i "72 on so you've either bought a DT2 or DT3 cylinder if it looks the same in the way it fits on, base gasket, head gasket etc. Or it's a DT2MX cylinder which looks a bit squarer in the fining, head fins are taller too if you have the matching head. Need pics please if pos. Only problem will be--if you 'do' have a "71 piston port DT1 7 go to fit a reed cylinder then there's a conrod length difference of about 5 or 6mm. Same problem doesn't happen with a 360 going from piston port to reed. Confusing myself now so i'll leave it at that.

5mm longer conrod for the DT1 with a 5mm lower piston from the pin which puts the top in the same place.

Offline dont

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Re: dt1 question
« Reply #11 on: December 07, 2017, 09:16:28 PM »
Found this on Ebay.
https://www.ebay.com.au/itm/New-Yamaha-Headlight-Bulb-CT1-CT2-CT3-DT1-DT2-DT3-RT1-RT2-RT3-175-250-360-400-DT-/281985258943
It is a sealed beam probably like the one you have but there is a list of other Yamaha's that share the same size light.
I may even order one for my RT3 and keep it as a spare.
......
I'd guess its wrong pattern for legal use in aus.

Offline sleepy

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Re: dt1 question
« Reply #12 on: December 08, 2017, 12:43:25 AM »
Found this on Ebay.
https://www.ebay.com.au/itm/New-Yamaha-Headlight-Bulb-CT1-CT2-CT3-DT1-DT2-DT3-RT1-RT2-RT3-175-250-360-400-DT-/281985258943
It is a sealed beam probably like the one you have but there is a list of other Yamaha's that share the same size light.
I may even order one for my RT3 and keep it as a spare.
......
I'd guess its wrong pattern for legal use in aus.

That could be a problem but the Ebay site gave a long list other Yamaha's that share the same lens which could help in finding something.
One would have to be pretty brave to ride at night with those 6 volt light these days.

Offline kenny

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Re: dt1 question
« Reply #13 on: December 08, 2017, 02:58:48 AM »
thanks for the link off the head light
the cylinder that is now on my dt1 is one without a reed , i bought the other cylinder as a spare
here are some pic s off the cylinder and the dt1






cheers
kenny

Offline sleepy

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Re: dt1 question
« Reply #14 on: December 08, 2017, 10:30:46 AM »
My guess would be DT2MX as there are no fins cut away for the side pipe.
Looks like a lot of work on the bike to bring it back to original.