Yamaha SZR 660 conversion to 350 YPVS - ( TZ250 replica )

[JanBros]

I am approaching the mounts fabrication in a different way, so I can continue without having to weld. I eventually might take the bike to a welder although it will be really not neccesary but for nice pro finishing purposes.

you realy consider not welding and riding it like this with all those cuts and sharp edges (those cuts up front are also prone tocrack) next to the "blocks" where all the stresses from the engine will be transmitted to the frame ?

on the other side, that big gaping whole in the frame behind the "blocks" won't do any good for the stifness of the frame. again a lot of stress right where you have made it the weakest at the sharp cutting edges.

You DEFINITLY need welding. And as you need welding, there would have been no need for those big blocks inside the frame, or the 3 bolts to bolt the blocks. You could have saved a lot on weight.

[evan_calgary]

Oh man, from an engineering perspective there has been so much damage done to the integrity of that frame. Please look into how the stiffness and strength is derived for a hollow box section frame. The mounting position is likely going to cause cracks which are going directly across the main spar of the frame. There will be additional vibration transmitted to those areas as well.

Was this not originally a cradle mount frame? Making a new cradle would have been a much better idea.

Engine transplant projects with the RZ/banshee motor are all over the web. This SRX frame looks very similar to the later TZRs. They essentially all require minimal modification of the aluminum frames with the worst being small u-shapes cut for carb clearance and ALWAYS heavily reinforced with welding and usually tempering afterward.

[MK]

If anyone fancies using the SZR frame for a project:
I happen to have one to let go for cheap $$. Only culprit: It's in northern Germany.
(For UK residents: I'll be at the 25'th AC RD rally in Derby in July and could bring it there)

[two-stroke-brit]

Oh man, from an engineering perspective there has been so much damage done to the integrity of that frame. Please look into how the stiffness and strength is derived for a hollow box section frame. The mounting position is likely going to cause cracks which are going directly across the main spar of the frame. There will be additional vibration transmitted to those areas as well.

Was this not originally a cradle mount frame? Making a new cradle would have been a much better idea.

I was thinking the very same thing.

[JanBros]

I seriously can not understand no one has made any comment on this for 13 days ...

it remindes me a bit of this built : http://www.kr-1s.co.uk/forum/viewtopic. ... 84&start=0 (I was being VERY nice to him in the beginning!)

allthough this SZR ain't as bad, I wouldn ride it

[Ricino]

Thank you all for the input regarding the frame, those are valuable considerations and I’ll definitelly weld everything for structural purposes.

I wouldn’t have done such a mess, but the SZR frame has some ugly, non symmetrical mounts (prepared for a 660 4t single) that I just couldn’t use to attach a cradle to. . So why did I choose this bike? Because here in Spain we do not have 3MA or 4DL bikes. And because at the beginning I thought it was going to be easier to accomplish, and it has been during the process that I´ve understood why so few people have done this conversion on a SZR (several Cagiva Mito 125 instead).

This frame derives from the 3MA and 4DL frames, but none of the original and symmetrical front mounts remain, which would mean piece of cake, as seen in other projects. The SZR has massive die-cast front mounts that I found out to be useless for this project.

Here is a pic of the original SZR 660 frame :

[evan_calgary]

Interesting frame. Quite similar to the TZR but much different in terms of mounts. I can see where the difficulty comes from.

[MK]

And not only the wrong brackets are an obstacle, the painted frame is a major PITA for welding because you'd need to get the whole frame cleaned...

I successfully welded Suzuki, Kawasaki, Honda, KTM and Zero ali frames and swingarms with AlMg5 rods. No additional treatment afterwards.
Some of it is still in hard motocross/supermoto use and didn't crack, yet.

[Ricino]

Thanks MK for your valuable input.

My intention is to bring it to a sandblasting guy, then to the welder and finally to the painter for satin black powder coating.

My question here is if the frame will withstand the high temperature during the painting process without warping. Any thoughts about this?

Edit: I’ve had some MX and trials alloy rims powder coated and they did not distort ...

[MK]

Definitely yes.

As you need to pre-heat the whole frame ahead of welding, it'll have to bear much more temperature there ...

[evan_calgary]

If by painting you mean powder coating then yes, there is no concern about the low temps the frame goes through to melt the polymer used in powder coating. It is of no concern and anyone who tries to tell you otherwise is a serious worrier. Powder bakes in ~15 mins.

[Ricino]

Thank you both MK and Evan!
Then...

1st - media blasting
2nd - quality welding
3rd - powder coating (satin black)

But I still have to solve the torque bars installation, which I believe fundamental to avoid undesired side effects...

[Ricino]

Hi folks,

Prior to welding...
Since I’ll take the engine off the frame for welding purposes... Is it advisable to put some additional spacers (I mean sort of mocking the engine case mounts) to keep the measurements in place due to a possible alloy distortion?

[MK]

Usually that's called a rig and fixes all attachment points.

In your case the spacers won't do nothing more than you could do with a 500gram mallet after welding....

[Ricino]

Thanks MK !
Rig... a new word for my limited English vocabulary.