1974 Kawasaki F11 Deuce Fifty aka: lil stroker

[LeVeL]

I'm introducing my build thread for a mild cafe treatment. I've always wanted a two stroke bike and when this came up for sale I couldn't pass it up. I pick it up with a title for cheap, overall its in decent shape. Nothing electrical works though the 6volt battery is hooked up. The bike runs but the carb leaks like a sieve. The petcock has a slow leak as well, just adding to the pile of gas under the bike. The tach doesn't work and the oil injection system needs help, although i think this one is just minor. The lines are clogged and crusty. so hopefully changing those will fix the problem.

I rode the bike around for 30 or so miles, the power seems ok for a little two stroke, but could be better. For the most part this bike is going to be a commuter. I would also like to retain the seat as is, maybe just a recover. I've already had the bike two up with my girl, and as we are both light (together not even coming close to 300lbs) it does just fine. I would like this to be a fun little scoot to take short trips around ohio on. If anyone has any info on these bikes I would greatly appreciate it, as google yields next to nothing.

on a side note, Im open to all ideas on what should be done. I've never owned a two stroke so anything helps me learn... ive got an expansion chamber, but was told the bike is ludicrously loud with it on. Don't know if theres any power to be had with it on, but after the carbs fixed im sure a test run will be in order

 

[perattzi]

Looks like a solid complete dirt bike...not sure it's the best candidate for a cafe though? The whole geometry is different than a road bike. I bet its fun as hell to blast around on though.

 

[boingk]

I've never owned a two stroke so anything helps me learn...

Righteo, first off you just need to give the bike a complete going over. By 'going over' I mean the following:

Change transmission oil & filter (if any)
Change air filter
Clean airbox, runners & carburettor
Return carb to stock specs
Install new sparkplug
Clean, lube & adjust chain
Check/replace battery
Remove exhaust and decoke.

Ok, done all that? Sweet. Wait, decoking the exhaust? Yeah, thats what I said. Simply remove the whole system and give a good rinse & shake with some methylated/denatured spirits and a handful of old change or washers. If you can unpack the muffler then do that, give a good rinse/scrub and install new packing. Done? Awesome. The reason I'm harping on this is because after so many years the stock pipe will probably be blocked with black fuel-oil grunge, and will rob you of proper power - especially the 'powerband' that all strokers are famed to have.

Fitting an expansion chamber will help with power, but its got to be designed to work with that particular model of bike - you can't just go and get any old expansion pipe and whack on there. They work by utilising the exhaust pulse to form a sonic shockwave, and this shockwave is reflected back up the pipe. Just as the cylinder is being closed by the rising piston, this sonic wave forces fuel/air mixture that has gone out the exhaust back into the cylinder, thereby giving a form of 'supercharging' effect to the engine.

So...fitting the pipe will help with power, but only if its specifically made for the bike. You will also have to rejet the carburettor, I'd budget anywhere from 1 to 3 mainjet sizes over stock. It may be louder, but this will depend on the silencer that you attach to it. The good news is that stock pipes on the old enduro strokers give a great spread of torque right through the rev range - try it stock first and see how you like it. It'll also be easier to get running well in stock form, and you can go from there if you want a bit more poke.

The oil injection system will need to be bled after you change lines. There should be a throttle-sensitive lever on it - move the throttle and the lever will move as well. This governs flow of oil from the pump - high throttle equals more oil. Let the bike idle and hold the pump lever at max flow position to bleed the system through. When the bike starts smoking heavily then you have it right. Hold medium revs to clear the engine and then try a few throttle bursts - no or little smoke when idling or at constant throttle and heavier smoke when accelerating or blipping throttle means that you've got it right.

Apart from that, I think you're good to go. You know what? I'm bloody jealous. Perhaps I should go and revive my poor little Kawasaki 100...

Cheers - boingk

EDIT: On the cafe front, you may be surprised by how well the stock bars work when taken off, stripped and put on backwards and upside-down. This is all I did to my little Kawa 100 and it looks pretty smart. Quite low bars in that manner, but it does make you feel a bit more confident through corners.

EDIT 2: Oh yes... these make about 24hp @ 6,000rpm, and have a stock top speed of about 80mph. Modifying the gearing will increase the speed at the cost of acceleration. Working it with mild porting & headwork, plus expansion chamber & carburettor tuning will see it pushing out a fair bit more than 24hp... I'd say that 30hp is a reasonable target, and that 36hp would be doable without getting too insane.