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Messages - John Orchard

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General Discussion / Just checking in .....
« on: January 11, 2024, 10:15:44 AM »
2 weeks no posts, just keeping things active :-) Come on Chaps, just talk anything VMX, I need my fix ;-)

General Discussion / Re: Any old boys still here ?
« on: November 17, 2023, 10:31:45 AM »
I first came here in 2010, when I retired from serious roadracing, but still have connections with a few from my motocross days, from 1974 to 1986.

General Discussion / Re: Any old boys still here ?
« on: October 20, 2023, 09:48:31 AM »
When did the forum start?

Tech Talk / Re: CR250M inlet port height different, why?
« on: September 09, 2023, 11:23:32 PM »
Lower ring gap

Oh that sounds boring :-(

Tech Talk / CR250M inlet port height different, why?
« on: September 08, 2023, 05:32:25 PM »
So here is another useless rambling post from me :-)

I've known for many years of the odd inlet port of the Honda CR250M, but I only just now wonder why? I guess I look at employing such trickery on another bike. With the top of the two inlet port windows at different heights, below is a link to the cylinder liner. I guess at a couple of the following reasons ....

* Added crankcase turbulence?

* Flow from each port directed in a different direction?

* With one port starting to close before the other, could it give a mild supercharging effect to the later closing window?

By all reports the CR250M was the fastest 250 in its time, the inlet port being the only thing that seems to stand out from the 250's, makes me wonder, hmmm.

Feel free to offer your own crazy ideas :-)

Hey Guy's, I want to purchase some parts from the US, the company that sells them does not ship to Australia, is there a company, or rider, that I could pay to purchase the required parts and post to me in Australia?

System problems? / Re: Is security certificate going to be updated?
« on: August 11, 2023, 01:50:48 PM »
Mine all good now, not sure if 'I' fixed it, I stumbled through clicking this & that on & off :-)

System problems? / Re: Is security certificate going to be updated?
« on: August 10, 2023, 10:27:53 AM »
Tried Chrome, still no.

System problems? / Re: Is security certificate going to be updated?
« on: August 09, 2023, 09:07:27 AM »
Nah I still have to go "advanced" to get in, I'll have to figure out my Microsoft Edge info.

System problems? / Is security certificate going to be updated?
« on: August 08, 2023, 02:04:48 PM »
See above :-)

This service bulletin for 1975 I think you may find handy.

That is interesting, thanks. I notice that the RM250A (70mm bore) has the same situation re ring end-gap.

Tech Talk / RM125S Piston rings without notch for pin, eh?!
« on: July 15, 2023, 09:06:13 PM »
I have some NOS pistons & rings to suit '75 Suz RM125S, the rings (the .60mm thick ones) do not have a notch where they end at the pins, with the standard size rings fitted into a new 56mm bore, there is a 1.4mm end-gap. I think that when fitted to the piston, and slipped into the cylinder, a minimum of 1.2mm gap is required for the pin thickness, so the 1.4 would allow them to not jam hard against the pin when hot.

What are your thoughts of running such a wide end-gap? I was thinking of running .25 over rings, and grinding an angle at the ring end, to minimise the end-gap, but I worry that a .6mm think ring does not leave much metal to handle the heat?

Has this matter ever arisen for RM125S owners before?

Anyone wanting a .5mm copper head gasket for a Suzuki TS125B ~ TS125ERZ ('77 to '82), the original gasket for the 1980 Honda CR125 is the go, part number 12251-466-000.


I was wondering if anyone has used a 1980 Honda CR125 copper head gasket, 12251-466-000, on a Suz TS125? Could anyone advise me of the distance from stud centre to stud centre? TIA

EDIT; Yes it is the same :-)

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