engine mods??

[renault_megane_dci]

Those dry clutch conversion involve a brand new crankcase cover.

I don't know about your bike but I will google Honda CB 450 dry clutch conversion at some point or ask the mecanic buddy who showed it to me.
His involved an hydraulic clutch actuator too.

[jkv357]

Originally Posted by renault_megane_dci

Those dry clutch conversion involve a brand new crankcase cover.

I don't know about your bike but I will google Honda CB 450 dry clutch conversion at some point or ask the mecanic buddy who showed it to me.
His involved an hydraulic clutch actuator too.

A friend of mine developed a dry clutch for his 450 race engines.

This is his Facebook page - https://www.facebook.com/pages/Team-...16916108330930

The photos of the dry clutch are from June 25th.

That would be a ton of work for this application.

[renault_megane_dci]

A dry clutch conversion kit (for a Honda CB 450) appears to be a little over 1000£

[bschloop]

Originally Posted by renault_megane_dci

A dry clutch conversion kit (for a Honda CB 450) appears to be a little over 1000£

Eek is right, that would cost more than half of what this bike has including everything I've done to it.

[renault_megane_dci]

Anyway, getting a second engine is your best investment as far as engine mods is concerned.

I have been thinking about overbore and it could be a good idea to boost torque if you keep the original head because the smaller the inlet tract vs capacity the more velocity in the inlet, the more torque.

[beatr911]

For the air cooled Yamaha series such as yours, the 230cc variant had the long stroke. There would be some comparisons needed to determine which piston/rod combination would work and you'd have to calculate compression. The only really viable way would be to have scored a great deal on a spare motor.

Coatings can help control heat. I'd probably just do the exhaust port as there is alot of heat transfer in that area.

Clean and smooth the combustion chamber and piston. Clean up both ports of casting and machining imperfections while you're in there

Advance the stock cams. One full tooth will more than likely be way too much. Try like 5-10 degrees of crank rotation. Experiment. There used to be an offset woodruff key available for the TW200 but I can't find it now. Just advancing the stock cams will boost low/midrange - just what you want.

Don't shave the head. Advancing the cam will cause the intake to close sooner and increase dynamic compression. Increasing compression also creates more heat, so if it's a concern don't make it any worse than needed. Also shaving the head will bring the cam closer to the crank, retarding the cam timing - not what you want.

Jet properly using an O2 sensor and an air/fuel ratio gauge. You need this if you've messed with the intake or exhaust. You can effectively use a narrow band sensor because you want to be very near stochiometric anyway, maybe just very slightly lean no more than 15:1 at the most.

If you can get away with only one compression ring it will reduce friction.

Use a new copper core plug. Yup, less resistance than even iridium, just won't last 50,000 miles - but who cares? Widen the gap at .050" increments until you detect a miss at high RPM and 100% throttle, then close the gap .050. That is your ideal plug gap. This works on nearly all I.C.E.s really.

For spare motors look for the Chinese clone made by Zongshen. These are bulletproof engines, just like the OEM Japanese engines and all parts interchange with Yamaha. Since they aren't imported anymore, watch CL for the supermotard Zongshen Sierra 200cc. They are often dirt cheap. I had one for over 6000 miles and loved it. There are reports of over 40K miles with only normal maintenance.

If you have a balancer shaft, remove it! It adds internal drag to the engine and removing it will also free up a little power. Just locktite every nut and bolt on your bike!

[renault_megane_dci]

Originally Posted by beatr911

Advance the stock cams. One full tooth will more than likely be way too much. Try like 5-10 degrees of crank rotation. Experiment. There used to be an offset woodruff key available for the TW200 but I can't find it now. Just advancing the stock cams will boost low/midrange - just what you want.

Don't shave the head. Advancing the cam will cause the intake to close sooner and increase dynamic compression. Increasing compression also creates more heat, so if it's a concern don't make it any worse than needed. Also shaving the head will bring the cam closer to the crank, retarding the cam timing - not what you want.

How about shaving the head and advancing the cam to restore initial timing ?
Wouldn't it be better overall (high rpm included) ?

Originally Posted by beatr911

Use a new copper core plug. Yup, less resistance than even iridium, just won't last 50,000 miles - but who cares? Widen the gap at .050" increments until you detect a miss at high RPM and 100% throttle, then close the gap .050. That is your ideal plug gap. This works on nearly all I.C.E.s really.

That's a good one, thanks !
Step one, tune carb and step two work on plug gap, right ?

[jkv357]

Originally Posted by beatr911

Use a new copper core plug. Yup, less resistance than even iridium, just won't last 50,000 miles - but who cares? Widen the gap at .050" increments until you detect a miss at high RPM and 100% throttle, then close the gap .050. That is your ideal plug gap. This works on nearly all I.C.E.s really.

What are your thoughts about bumping up the heat range over the stock plug because of low RPM and light load operation?

The stock heat range factors in a wide range of conditions, including extended high RPM running, to ensure safe maximum temperatures. Consistently running much lower RPMs and loads should put the temps much lower than optimum with the stock heat range - you'd think.

[beatr911]

Originally Posted by renault_megane_dci

How about shaving the head and advancing the cam to restore initial timing ?
Wouldn't it be better overall (high rpm included) ?

Yes you could do that to increase compression and restore the cam timing to stock. He wants to boost low/mid output though and is not interested in high rpm. So just advancing the cam will increase both compression and low/mid output.



That's a good one, thanks !
Step one, tune carb and step two work on plug gap, right ?

Yes. But depending on how finely tuned you want to go, a larger gap will also burn a very slightly leaner mixture without misfire. So jet (with O2 feedback device), tune plug, try one step leaner (with O2 feedback device). We're really splitting hairs here so it's probably only beneficial if you already have the leaner jets for the last step. Humidity, barometric pressure and temperature also play a role and will adjust your mixture a tiny bit for you.

Also, carfully cut back the ground strap on the plug so it covers about 1/4-1/3 of the center electrode. It exposes the spark a little more. Google pictures of the Autolite AR103 sparkplug. The key for our use is the ground strap design. This plug alone was good for about 4% or ~1.5mpg over the double planinum plugs on my Focus.

[beatr911]

Originally Posted by jkv357

What are your thoughts about bumping up the heat range over the stock plug because of low RPM and light load operation?

The stock heat range factors in a wide range of conditions, including extended high RPM running, to ensure safe maximum temperatures. Consistently running much lower RPMs and loads should put the temps much lower than optimum with the stock heat range - you'd think.

I dunno. Heat ranges are something I don't mess with unless there is a fouling problem or burning. If anything, it seems a slightly cooler running plug at light load would be an asset if the compression was increased at all as has been discussed. One less thing to be a glow plug and cause pre-detonation or inconsistent flame spread.

I'm sure there is someone else that knows a whole lot more than me about heat ranges, and any directly attributable performance benefits within an acceptable range.