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Topics - John Orchard

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Yamaha / Yam clutch spring specs- 90501-20122 & 90501-20124 ?
« on: March 02, 2019, 12:59:18 PM »
Anyone with a range of Yamaha Clutch springs in stock be able to tell me the difference the following two clutch spring parts?


They both are listed for  a great many model Yams, both are listed for DT1 but one is listed for RT1; if one is a little stronger I'd like to get that one, TIA (Thanks In Advance).

Tech Talk / Trying to find port timing diagram for a DT1MX.
« on: February 27, 2019, 07:05:15 PM »
I'm still having no luck finding a port timing diagram for a Yam DT1MX, could anyone give me any leads please  :-)  TIA

. Yam DT1.
. PVL ignition 1.8mm advance, great spark.
. Radically ported cylinder, intake port lowered 4mm.
. GYT high comp head.
. Mikuni VM36
. Expansion chamber.

She no starting, not even a kick when spraying aerostart down the plug hole.

I'm thinking maybe the radical porting is not condusive to kickstarting speeds? With such delayed intake closing, maybe any fuel charge is being pushed back out?

Can PVL ignitions have good spark out of the cylinder but not under compression?

I would appreciate any ideas, (my brain hurts) thanks :-)

Never before have l been stumped like this.


Yamaha / Motocross seat conversion for Yam DT1?
« on: February 14, 2019, 10:06:36 AM »
Anyone got any ideas (or even something for sale?) for a narrower & taller seat for my race DT1?

Thanks in advance :-)

Tech Talk / DT1 clutch push revisited / update.
« on: February 12, 2019, 01:20:12 PM »
Sorry to have to bring up this subject again, I did a lot of searching on the site, there were two options suggested for a replacement for the DT/RT1,2,3 clutch push mechanism

RD250LC - 4L0-16340-01 & GSX600F - 23200-31300

Who has tried what and what finally worked-out to be the best option? I have broken the plastic worm-drive, plus its holder (with adjustment screw & locknut) is bent out of shape.

I have money ready for Express Post, I have rebuilt the bike, just need this part so I can test; I'm getting a bit amped to try  ;-)

Wanted / WANTED, Suz TM or TS 250 piston.
« on: February 07, 2019, 10:13:57 PM »
Anyone have a Suzuki TM250 or TS250 .5mm over piston they would like to sell?  The following part numbers & models, these are the later model pistons that use the thinner rings, thanks.

12110-30510-050 TS250 '77 to '81
12103-30820-050 TS250 '77 to '81

12110-30001-050 TS250 '71 to '76
12103-30810-050 TS250 '71 to '76

12110-30010-050 TM250 '74 to '75

Tech Talk / Fuel resistant glue for bonding rubber to metal?
« on: January 28, 2019, 06:52:48 PM »
I have to glue a rubber seal into my metal fuel tank cap, anyone have experience with a particular glue?

Wanted / WANTED- 5x4 pattern knobby, 4.50 or 5.00 x 18.
« on: January 26, 2019, 10:38:29 PM »
Hey Guy's, l'm trying to find out what vintage style motocross tyres are available? Something like a Pirelli Garacross in a 4.50 x 18, or Cheng Shin C755 in a 5.30 x 18.

Anyone got any ideas where l might purchase a new tyre from?

Best rear tyre l ever used, Trelleborg Tenmaster 4.50 x 18, on my '83 Hon CR500. l see overseas that there is a Mitas look-alike, l wonder if it's any good and if it is imported?

Yamaha / Straight cut gears DT1, where?
« on: January 25, 2019, 04:51:50 PM »
If I wanted to replace the primary drive gears on a DT1 with straight-cut, where would I start looking, anyone know?

General Discussion / ebay calculated import charges increase.
« on: January 23, 2019, 10:16:18 AM »
Hi Guy's, l thought that when ebay started adding 'import charges' to the total purchase amount, l thought it was 10% but when l put stuff into my cart now it is calculating about 21%. Am l going crazy or am l now ceasing any purchasing from overseas?

eBay Finds / Rubber inlet manifolds, 2-bolt, suit 36/38 carb.
« on: January 22, 2019, 10:56:30 AM »
I just bought a set of these inlet manifolds (4) for the VM38 on my bike, the set cost $35 landed, so have spares if I need them  :-)  The bolt holes are for 6mm bolts but I files them out for 8mm's.

Wanted / WANTED - Damaged fuel tank with screw-on cap.
« on: January 16, 2019, 11:38:27 AM »
Hey Guy's, I want to replace the flip-up cap on a fuel tank with a screw-on cap (maybe one with a breather tube outlet?).

Anyone got a damaged tank I can buy and cut the filler neck out of? Need an inch or two of decent material around the neck; I don't want to weld too close to filler neck and distort it.


Competition / ls a Pre 70 bike legal with a plastic fuel tank?
« on: January 15, 2019, 10:18:04 PM »
I really want to stay 'period' but if l have to .......

For Sale / DT1 68 ~ 70 swingarm bush collars.
« on: January 15, 2019, 08:44:52 PM »
Swingarm pivot bush collars x 2  To suit 1968 to 1970 only,  Part number 214-22124-00,  $50pr plus postage.

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