I've just completed a 200 conversion on a TY175,anyone out there got sugestions on carb size so i can get the most out of the bike,also dimentions for swing arm lengthening and shock reposition.Cheers.Chris

has the 200 kit made much difference? Also have you upgraded reed valves?

Apologies if vim asking before you have had it running!

how did you do conversion, what size piston and what from ? I have had mine bored to + 2mm to make it roughly 185 and with some other tuning done I felt the standard carb was a bit on the small side and bike did not rev out easily although ok at bottom end, I fitted a DT175 carb which is a 24mm mikuni vm (wanted to keep it all period, have a bit of a bee in my bonnet about monos converted to twin shock etc), although this has taken a little setting up it is now as good at bottom end as the original 22mm vm but with better mid and top end (I think ! don't forget testing performance of bikes/carbs is very subjective) I am now looking for a genuine 200cc conversion, told by John cane at trials and trails uk (think thats the right name) that he is shortly going to be offering a full 200cc conversion with some good porting work.

I tho't John Cane was already offering that kit - with 71mm piston (= 198cc) & porting developed by Reg May back in the day.

Worth remembering that some people have reported a problem w the kickstarter breaking when you go for the big-bore kits.

I've been told the barrel,head,gudgeon pin bushes and spacer are original shirty,i put a new piston and rings etc in,which are dt250mx,the piston needed 5mm taking off the skirt,and the headgasket needed tweeking.I aim to start it sometime soon..............when i get over the first kick nerves!

Thats the kit I was told would be available soon ? the full 200 (Ok 198) with porting by reg may, but nothing on webiste so assumed its not yet available, with a standard ty/dt250 piston it takes it to abouit 192 ? can't remember for sure but it is not full 200 either way. anyone know if it is available from John cane (suppose I should ring him ?)

I've just completed a 200 conversion on a TY175,anyone out there got sugestions on carb size so i can get the most out of the bike,also dimentions for swing arm lengthening and shock reposition.Cheers.Chris

I've just added 22mm to my swinging arm, managed to cut up, just forward of the chain adjuster stops and across under the shock mounts, then added the plate in.

This has left the rear shocks in there standard position, but with the axle that much further back, it's made the action so much better.

Climbs a treat now, no more running out of grip trying to keep the front down.

Didn't even need to lengthen the brake torque arm.

For a carb upgrade, I've forked on one of these (add around

Hi all,

One reflection about big bore conversion using 250cc pistons; different wrist pin diameter TY/YZ/DT 175 vs TY/YZ/DT 250.

Do you know if this conversion incl change to none 175cc rod or machining of rod small end for 250cc wrist pin?

Forged pistons for mid/late 70

I know that they fit the 250 piston by bushing the small end down to the 175 size gudgeon pin, I am still waiting for a good 200cc kit including porting and head mods (which must be done to make conversion work properly) but have yet to find anyone that can do the kit including porting head mods etc, would be willing to pay a decnt price for the right work.

Thanks ausy,

Ok, bushes machined for cirlclips, robust enough..?

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If you prefer first class 2-t trials tuning (modern clubman) of a 175cc Im convinced several experts are offering what you need in the UK! Shipping to US is not cheap but BJ Racing are skilled..(Im planning to focus on TY175 engine rebuild and cost efficient improvements...My TYR have lots of improvements providing impressive performance better than a 3-4y modern spanish. Std TYR porting and std ign-84.)

Honestly I have limited experience from 60-70

how did you do conversion, what size piston and what from ? I have had mine bored to + 2mm to make it roughly 185 and with some other tuning done I felt the standard carb was a bit on the small side and bike did not rev out easily although ok at bottom end, I fitted a DT175 carb which is a 24mm mikuni vm (wanted to keep it all period, have a bit of a bee in my bonnet about monos converted to twin shock etc), although this has taken a little setting up it is now as good at bottom end as the original 22mm vm but with better mid and top end (I think ! don't forget testing performance of bikes/carbs is very subjective) I am now looking for a genuine 200cc conversion, told by John cane at trials and trails uk (think thats the right name) that he is shortly going to be offering a full 200cc conversion with some good porting work.

DT175 MX carb is the way to go , on mine a 200 conversion was too costly/complex, so had the crank rebuilt , new mains and seals and a fresh top end - even though engine was "OK" bored to 2nd oversize, new yam gen piston, and re-bult wes exhaust - when finished pulled like a train, compared to a std 175 - (I had both at the time), Birketts, who opened and re built the exhaust /silencer combo, called me to ask what I had done to it (honestly ) .

200 conversions are rightly lusted after , but sometimes the basics, on what are very old 2 stroke engines can make a huge difference, - ask any road racer .

best post yet on the TY175/200 issue, could not agree more with you, I raced a TZ350E back in the day, and glad you said the 200 is rightly lusted after, I have been prusuing this avenue for a while with lots of negative comments about the 200 being worse than a 175 (171 actually if memory serves), and have always said that a bigger capacity engine, especially when looking for some more torque, will always out perform a smaller one, if and this is the big one, if it is done right.