1977 Suzuki A50 build is complete! (Ha!)

[Raizer]

I paid for a carb with the quick change jetting cap, I'm going to use the quick change cap!!

Done something rather strange for this project today, I actually took it out for a half decent ride around town!!

2 Monsters!

Also think I've sound a solution to my piston slap woes, have come across multiple Taiwanese kits

Have put my hand up for 2 for now, first one is going to just be a bit of an experiment test bed, going to attempt removing the liner, adding the extra ports like my current one and seeing if I can turn a head and get it to run.

I know with the Taiwanese kits that I shouldn't expect great things from the piston and to keep the compression on the lower side of fun, but if the liner is decent enough there is stock (47mm), +0.50 and +1.00 TKRJ pistons in stock with a supplier here in NZ.

If I manage to pull that off then the second one will be getting a new Wiseco or Melling cylinder sleeve and 49mm Wiseco piston and another new head.

[Raizer]

Casting doesn't look too bad, nowhere near Suzuki factory standards, but better than some cheap kits I've seen at least.

Suzuki are cast with 72CM³ rather than 78 and the font screams China to me.

Porting and piston, again not great but not terrible

Lined the piston up with the floor of the exhaust and transfer ports about where I thought BDC would be

Hmm something isn't right there!!

Fitted to my old engine, at BDC there's an issue

The 2 boost ports are pretty well lined up where they should be, but the exhaust and transfers are about 5.68mm higher than the piston edge!  

Edit: It still bugged me that my original piston that is meant to be a +1.50 from an old TS75 doesn't match up to what's listed for TS/TM/RV75 or A80 models which are all meant to have pretty much the same piston.

So I pulled my top end off yet again, quadruple checked the measurements and spent the couple of hours reading piston catalogs again, and well it's paid off as I have found only one piston from TKRJ that matches almost every measurement!!*

I give you the piston from a Yamaha YG-80!

Even better news is that I seem to be able to order them in both 1.75 and 2.00 oversize directly from TKRJ in Japan.
Another giveaway is that all three TKRJ pistons for Suzuki have notches for getting the pin clips out, but none of the Yamaha ones do.

 

*The only measurement that doesn't match up is the overall length, mine is 2.2mm shorter and has some kinda obvious file marks where it has had clearance added to clear the crank webs at BDC ha

Edit 2:

Toshihiko at TKRJ pistons got back to me informing me that they don't have any stock of the 1.75 or 2.00 over options, but they have the 1.50 I've already got readily available.

Figured that another 1.50 would be a waste of time, but I still ended up asking him for exact measurements of the piston, they are between 48.450 to 48.470.

My current worn out 1.50 measured up at 48.305 and the cylinder at 48.495.
So worst case fitment is 48.495 - 48.450 = 0.045 clearance in the cylinder! So it would actually need a slight hone to fit!!

RESULT!!

[Raizer]

Well that didn't go well!
Forks started bottoming out pretty hard, maybe a K later on a stretch of undulating gravel Rd they bottomed out and stuck down, front went light and the wheel flicked out from under.






Also it just hasn't got the torque range to pull 5th gear, maxes out 4th at 80-90k at ALL the rpm, change to 5th and it drops off pipe hard and sits on 65-70.

Discovered on a steep downhill it will come on pipe eventually in 5th, but it'll never get there without a big ass hill or a typhoon level tailwind!    

New piston is almost here, so I'll set it up again and just keep it as a city pester as it's a blast around town.

Thinking CG125(?) disc front end and a few other improvements will be a good idea and also have thoughts on building something a bit more serious with my spare rolling frame. 

[oldgeek]

Sorry man, that really sucks! Glad you are pretty much ok though.

[pinkscoot]

I hope you're alright. The rest is fixable.

[aeroxbud]

That's a sad sight. I'm sure you can fix it though.
Would going up a couple of teeth on the rear sprocket not help it use top gear?

[Raizer]

It's sure worth a try changing the sprocket, might make first a bit too short but that'll be live-with-able.
It's a thing with these Suzuki's having the last gear a bit tall, I know a few guys with the A100 that struggle to pull in 4th (the 100cc is 4 speed)

[viggy17]

Hi Raizer, I’m resurrecting your old post if I may 😝
Amazing work, WAY out of my league. But I have a question for you on the rotary valve. How many degrees did you trim off each side with the punch mark facing up and the half moon downwards? I’m trying to be careful I get the orientation right! I have a diagram for an A100 but it looks like the larger trim is on the other side to yours (I would have attached but I don’t get the option). Thanks

[motobaz]

Awesome build. What tyre sizes did you run with? Same front and back?