new 50 (maybe)

[cotswold]

The story is I sold my little Honda 50 onto Terrene as I wanted to build this next one. If I had kept the Honda I would have spent too much time I do not have making constant changes to it and the project would stay under my shelf.
The plan is:
I found a very cheap SR50 Aprilia on TM it had a big bore 70 kit and all the Malossi variators and electronics but ran like a dog so it's owner gave up.
1st job was to bin the cylinder and find a 50cc one. I ended up with an RS50 cylinder that the boys from ESE had sat on a bench and have spent quite a few hours matching it to the cases and vice versa.
I also have another aluminium Aprilia cylinder with twin ex ports that fits as well.
Port timing using the Aprilia piston was wild so a Barikit one was found and it is so much better.
The Aprilia piston is too long above the pin and gave me 204 and 140*
I have a semi down draft carb but still need to find a manifold.
I plan on rebuilding the crank, throwing in new bearings and seals and giving it a nudge, what could go wrong

[cotswold]

I'll chuck up photo's as I go.
I think it's a good job I have mates with unwanted parts as this could be doomed to fail, but if it works I am after 14-16 bhp and cvt, not asking for much. If it does go belly up all parts will be recycled I'm sure

[speedpro]

The Aprilia piston is too long above the pin and gave me 204 and 140*

A shorter piston will give you even more. It won't have to move so far ATDC before a port is exposed. If you set the same deck height for both pistons of course it won't make any difference.

[cotswold]

A shorter piston will give you even more. It won't have to move so far ATDC before a port is exposed. If you set the same deck height for both pistons of course it won't make any difference.

I had to lift the cylinder nearly 3mm with the Aprilia piston but just a base gasket using the Barakt

[cotswold]

Bones are being fleshed out.
a little cutting and maybe a different front end

[cotswold]

https://www.youtube.com/watch?v=uCEvBGT8twM

[cotswold]

been doing a bit of work on the CVT project, I rebuilt the crank with a bit of help but it is still a piece of crap but I'll try it out before going to the trouble of finding a better one, I needed to make an adaptor plate to fit the carb and manifold so been busy in the shed with my trusty Dremmil and a drill

[Tbh37620]

Very interested to see how the mounting of the fairing/seat comes out and also how to fab up the foot pegs :2thumbsup

[Drew]

Someone buy this man a holesaw set.

[cotswold]

[QUOTE=cotswold;1131008586]The story is I sold my little Honda 50 onto Terrene as I wanted to build this next one. If I had kept the Honda I would have spent too much time I do not have making constant changes to it and the project would stay under my shelf.
The plan is: WAS
New plan.

I was offered a pretty hot NSR50 engine along with so many parts that it all weighed 180kg. The motor ran in a series in the Netherlands and has been developed by its ex owner Jenne Smit.
Not sure if any of you remember but Jenne gave me plenty of technical advise when I was building my NSR engine, I managed to get 14bhp with a 28mm PWK using the cast iron Honda cylinder, Jenne used an aftermarket aluminium cylinder and a tiny carby as was their rules and has a dyno pull of 17bhp.
It all turned up in a crate a few weeks ago and myself and ESE (culley) have started putting it into an NF4 chassis that had previously held a 12bhp RG50 motor.
The photo's are it's progression.

[cotswold]

The forks came in the crate and will be added in due course as they are an obvious upgrade on the NF4 ones.
I'll keep putting photo's up as it progresses.

[F5 Dave]

A Honda in a RS frame? That's novel for a 50 . Should be a weapon. What sort of revs and power spread?

[cotswold]

A Honda in a RS frame? That's novel for a 50 . Should be a weapon. What sort of revs and power spread?

I've lost the Dyno pic that Jenne sent me but I'll post up the one we do on ESE's machine when we get it running, I'm a bit excited and nervous at the same time.

[cotswold]

I'm pretty sure this is the one I have been searching for

[F5 Dave]

It's not revving as high as I would have thought. My pet hate though is a graph that doesn't start at zero.

[cotswold]

It's not revving as high as I would have thought. My pet hate though is a graph that doesn't start at zero.

Dave, if I ever let my 50 get to zero on the track you have my permission to kick my ass, I have always wondered why TZee lets his bikes off the power when he dyno's them, in real life you keep them on the boil at all cost.

[F5 Dave]

Um, I just mean if the graph starts at zero every time, even if the curve starts at 8000 when you push the button at least you can see on the same scale rather than one curve started at 10,000 which always looks betterer

[cotswold]

Um, I just mean if the graph starts at zero every time, even if the curve starts at 8000 when you push the button at least you can see on the same scale rather than one curve started at 10,000 which always looks betterer

Ah so ..........

[TALLIS]

How's this build getting on Tim?
Spent a little more time on mounting the old am6 in the frame today.
Had it running, but it won't get on the pipe for some reason? No idea why.

[F5 Dave]

Um. . Jetting?

[Tbh37620]

How's this build getting on Tim?


Curious also, my dream bike for the kart tracks has always been a GP style frame/riding position with a hot rod scooter CVT engine.

[cotswold]

The first time we put the new 50 on the dyno it made 14 and a bit on a OKO 24, the fueling was a bit off and it didnt sound awesome so I returned today with a genuine PWK 28 nand set about jetting it on the dyno. After a few changes and a little drilling out of the air correction jet it ran pretty well up to 16.1 BHP at the wheel with 6.7 torques to go with it. Pretty damn pleased, the next thing will be to replace the piston and rings and the insert as both are a little battle worn.

VIDEO https://www.facebook.com/tim.coopey/videos/10218337840351113/

[F5 Dave]

Air correction change for response or spread at full? Should be fun on the track.

[cotswold]

Tz was trying to fatten up the midrange I think, I spent most of my time changing jets so can’t remember how the curve was affected

[cotswold]

My 50 is pretty much ready for the GP
I have a question for the 2t gurus, I have some exhaust spacers to make the pipe longer, has anyone done any testing on this? The pipe seems to be working ok as is but just keen to know what happens when you lengthen it?
I have also replaced the complete braking system on the front as it had a nasty tendency to throw me on my face at completely random times, if I trail braked in 90% of the time it was fine but on occasion it would lock the front wheel up and spit me off with lightening speed, no indication no warning just a puff of tyre smoke and bang. It had a after market wavy disc that had some serious slots and the theory was that maybe the pads were jamming into them, I had previously taken the caliper apart and cleaned n lubed it, thought I had it fixed until it bit me again in race 2 at Edgecombe. NF4 set up by the way, has anybody else had this happen?
Looking forward to the GP as I get to ride ESE's brilliant 110 and my ESE Smit50 both in NF4 frames.

[F5 Dave]

Cool.

Header extension will only really work if your original header is too short, if its already close it will just make peak revs lower and all that entails. I had a pipe which adding an extra gasket did help so I extended the manifold.

Brakes, well these are likely old so you need to revisit everything.

I hate Chinese discs. Check with pointer taped to fork that it is straight. I'd ask how worn rivets are on an old disc, but. . .
Try find a std CBR400 disc I think worked, plenty of Honda crossovers.

Take caliper apart, pump pistons out, flick out seals carefully with flat pick. Clean up and clean the grooves the seals live in. They grow white oxide and that has to be removed or it pushes the seals out. Carefully pick out with flat pick trying not to scratch the shit out of it.

A brass brush on a dremel can make good job on this. Inspect bores. Any corrosion? Light wet and dry fine with lube. Brake clean spotless.

Honestly appraise the pistons. Clean up with autosol. Maybe carefully with scotch plastic pad. But anything going into the seal area needs to be mint. You can buy aftermarket pistons and seals.

Inspect seals with magnifier. Often the main flat seals are fine with sharp edges but the dust seals are important too and need to be square and unworn. Replace if in doubt.

Pads worn angled, replace. You can buy aftermarket pad retainer pins, take the old ones into shop that has decent dirtbike spares range. Check parts diagram and replace missing springclips or rebend them so they push lightly on pads.

Check there isn't too much wear on the sliding section and it moves freely. Should be lubed with rubber grease or high temp copperslilp.

Inspect brake line not manky.

Last but not least, the master cylinder. The wrong lever will only just open the return hole as it is always slightly on. If this is the case, when it gets hot it can block the hole enough to close it or at least leave it on a second longer perhaps.

Make sure there is some play. I've had to dress to make clearance before. Check correct bolt at pivot and lube. With this all done check the lever stroke. It should be smooth and stepless . Any jerkiness is trouble.

Inspect master rubber doofer on the cap for tears and clean out the vents in cap.

Fill with new fluid, bleed.

All this can be done in a night, likely trip to bike shop or online if time, and another put it back together session. All easy as if take your time. All is better than crashing.

[TZ350]

Take caliper apart, pump pistons out, flick out seals carefully with flat pick. Clean up and clean the grooves the seals live in. They grow white oxide and that has to be removed or it pushes the seals out. Carefully pick out with flat pick trying not to scratch the shit out of it.

Last but not least, the master cylinder. The wrong lever will only just open the return hole as it is always slightly on. If this is the case, when it gets hot it can block the hole enough to close it or at least leave it on a second longer perhaps. Make sure there is some play. I've had to dress to make clearance before.

+1 ....... :niceone: