1984 Yamaha CA50 budget build!

[markopollo]

well, i cant leave anything alone, and when you get some $$$ form parting out a bike, you know i gotta spend it somehow. 

i figured id give myself a challenge. I have this yamaha CA50 that has a LOT of miles (id guess over 9000) as i got it from the son of the orignal owner, who daily drove it since new, and only recently stopped driving about 2 years ago, thats when i picked it up on craigslist last year. 

now this thing stock isn't a performance machine at all, i plan to change that (kinda) i want to be able to hit 40-45mph, now that sounds slow, butt keep in mind, nearly 40 year old bike with ZERO aftermarket, so this will be fun!

first i installed a pod filter, went from 20mph (not making this up, 20 is all she wrote) to 25mph. 

next was the stage 6 minarelli vertical exhaust. the most recent edition (got it done bout a hour ago) and after a rejet it was a BLAZING 32mph! 

next i plan to shave the head, install a new drive belt and play with the roller size (believe there too heavy, as the pipe kicks in at about 28mph), possibly mess with the porting or make a revplate. 

should be a fun one!! 

[markopollo]

i ended up having to space out the exhaust to clear the kickstand and the suspension, also removed the muffler holder for additional clearance.

[drc174]

Love the CA. I need the side cowls if you ever decide to...

[markopollo]

hehe, not yet.

i was about half a second away from cutting them up to clear the muffler, but then I realized that I could just bend the muffler away instead.

I'm wondering if a Minarelli vertical cylinder might fit on this, anyone got an idea on the stud spacing?

[drc174]

It honestly should. I have the OG motor apart in a box, if you ever wanna do some measuring let me know, instead of ripping yours apart.

[markopollo]

actually, any chance you could get me the reed block bolt spacing and the cylinder stud spacing?


another update:

turns out the stage 6 exhaust i bought was a EU restricted type, since i bought it from scootertuning.ca (a great group of guys btw, eric and the team got great service going on! definitely will be purchasing my products from them now on)

the exhaust restricted had a circle less than 1/2in around! no wonder the pipe felt like it wasn't kicking in. bashed that crap out with a screwdriver and pliers (as my dremel is out of service)

also sealed up the motor mount flange spring thing, as it was leaking pretty bad. currently letting the high temp RTV set for 24hrs. lets hope it seals up!

[markopollo]

well got impatient and test rode it anyway, and WOW, what a difference, i had to up jet to 80 to get it to run good.

does about 35-38mph flat, but it if i go downhill and then flat it can maintain about 40-45mph!! as the speedo maxes out at 40 but it was going past that (where my key is)

pipe is sealed pretty good (my test way is to block the muffler and if it dies i consider it sealed)

going to order a couple of lighter rollers and see what it likes. this pipe is definitely geared towards higher rpm builds.
might have to up my goal to 60

[aeroxbud]

Great results so far.
I like the pro replica exhaust. It does need carefully setting up. But once dialled in, gives good performance. Peak power is about 9,500RPM.

[markopollo]

Dec 6, 2020 16:40:05 GMT -5 aeroxbud said:

Great results so far.
I like the pro replica exhaust. It does need carefully setting up. But once dialled in, gives good performance. Peak power is about 9,500RPM.

now if i can ask, by peak power is the maximum total pipe rpm or just the maximum power?

for example, the pipe "peaks" at 9.5K but still produces power to 10-11k? or does it just totally drop off after 9.5?

and, i got the veraitor apart, what's weird is that it has some kind of large rubber oil seal around the backplate and then a brass cylinder connected to the varaitor.  im wondering if its some sort of restriction. 

but i measured the rollers, they weigh in at 6.85G so im guessing 7g new. They do have a flat spot, but thats to be expected after possibly 100k miles (just guessing, if you daily it for 30 years) 

good thing is that there the common 15X12mm. so i ordered up a tuning set. 

ill start with 6 and work my way down. guessing 5.5 or 5.25 is going to be the best for me.

[markopollo]

Couple of late night photos. 

Exhuast hangs low, scraps if i lean too low. 

Ended up using some Velcro and exhaust wrap. Should be good enough for me.

Also some pics of the rollers.

[aeroxbud]

It will still rev over 9,500 rpm. Here is a graph. www.pedparts.co.uk/c/asset/sports-pipe-blog/70ccPolini.png

[markopollo]

Alright, looks like 9.8ishk is the limit before it totally drops off. By ear im not pulling anywhere near close to that.

Ill need to get a tach for it, but first I gotta get the rollers tuned.

[190mech]

You will need to do some serious port work along with squish adjustment and carb/reed tuning before you will get that stock motor to rev like that!Look around the web for A Graham Bell's Two Stroke Tuning book,its quite dated,but fits our scooter engines well!!

[markopollo]

Dec 7, 2020 18:39:34 GMT -5 190mech said:

You will need to do some serious port work along with squish adjustment and carb/reed tuning before you will get that stock motor to rev like that!Look around the web for A Graham Bell's Two Stroke Tuning book,its quite dated,but fits our scooter engines well!!

yea that's what i figured, im guessing im near the 7k range by just the ear. i also saw the other thread on this scooter, seems like the stock veraitor doesn't have very aggressive ramps, and a jog one should work?

ill hold off on porting the cylinder until i can get another one as i dont really want to screw it up, and since i dont know if a BBK kit would work (not sure if its the same stroke and bolt pattern as this one) 

might make a revplate if i got the time, and reduce the squish clearance. 

[markopollo]

well, installed the 5g rollers and removed the big oil seal thing, i believe it just restricts the movement of the variator and wont let it go use the full operation of it.

revs seem to be higher, but it's like a 2bump kind deal, it revs up, then after 10-15mph it drops back down, then up again once it hits the pipe, I believe this is due to the contra spring being too soft and allowing the variator to move to a higher gear too quickly, or the engine isnt producing enough torque to get past this.

top speed is similar, mostly 38mph now. still can maintain 45mph if i go down a hill and hold it wide. this could be due to the engine not producing enough torque or the contra being too light.

another weird thing is that i can hold 45, but if i close and open the throttle it bogs down like its lean until it picks back up again.