Having trouble mounting a 2 stroke onto this frame

[Gavin67]

The down tube is an oval shape, which is my main problem. The engine mounts have a shape that is complementary to circular down tubes. When I try mounting the engine it tends to slide and mostly tip to one side no matter how tight I make the brackets.

What can be done?

 

[FurryOnTheInside]

The V angle of the frame is very unlikely to be correct anyway, so even if the tube was round, and the same diameter as the front mount, the engine would still rest on one sharp edge of the front mount.
There is some excess material in the mount so it is okay to grind some away to reshape the mount and change its shape and angle.
The studs will not be perpendicular to the downtube, but there's a few people building with studs or u bolts not perpendicular to the tubes and it seems this is acceptable. You may want to find some tubing to cut a wedge shape to keep the lower strap part of the clamp pressed evenly against the downtube.

 

[crassius]

I would just put a piece of PVC between motor & frame, and if needed, I'd cut a couple longer mounting studs with perhaps another piece of PVC at bottom strap.

 

[gary55]

The V angle of the frame is very unlikely to be correct anyway, so even if the tube was round, and the same diameter as the front mount, the engine would still rest on one sharp edge of the front mount.
There is some excess material in the mount so it is okay to grind some away to reshape the mount and change its shape and angle.
The studs will not be perpendicular to the downtube, but there's a few people building with studs or u bolts not perpendicular to the tubes and it seems this is acceptable. You may want to find some tubing to cut a wedge shape to keep the lower strap part of the clamp pressed evenly against the downtube.

Show him how you did the head mount. Might help him stiffin things op a little.

 

[FurryOnTheInside]

Show him how you did the head mount. Might help him stiffin things op a little.

It might do, I think it would be a good thing to do on most frames, but he'd have to cut some channels in the automotive exhaust clamp to let the top tube cables through.

I'll see if I can find the pictures of my downtube mount.. I corrected the problem of the studs not being perpendicular to the tube but it involved raising the engine up on top of the plate and automotive exhaust U-clamp. I needed to do that anyway because my downtube is very wide. If you have a narrow enough downtube then I would still recommend that you just grind out the engine to match the tube shape and angle and don't worry about the angle of the studs.
https://motoredbikes.com/threads/front-mount-with-plate-angle-mismatch.50575/

When I was making the head steady I had to shape a couple more automotive exhaust U-clamps to fit the oddly shaped tubes, and again I filled the bracket with epoxy after shaping the metal (on a bench grinder and then a little bit with the dremel) to fit well.

Head steady (final version?)

• FurryOnTheInside
• Oct 1, 2017

The proper version of what I wanted, now joins the top tube and down tube of the frame, and...

Downtube mount saddle

• FurryOnTheInside
• Sep 18, 2017

The saddle part of a automotive exhaust clamp, with epoxy resin (filled out with a bit of the...

 

[Steve Best]

Godzijdank you have started building Furry!
Lots of great ideas and pictures too!

 

[FurryOnTheInside]

Godzijdank you have started building Furry!
Lots of great ideas and pictures too!

I've started test riding, breaking it in. Not this weekend though- spring tides and 70mph gusts.. **** that I'm staying indoors!

 

[Gavin67]

Thanks guys, I was able to mount it properly. Only problem now is that the carburetor does not fit into my new frame so I will have to get a offset intake manifold. Is there any disadvantage to using something that is offset and longer than just having the carburetor directly on?

 

[FurryOnTheInside]

No, it's fine. Actually longer (up to a point) is supposed to be better for low RPM torque.

Ideal length of intake

• FurryOnTheInside
• Sep 11, 2017

If the ideal intake length from slide to piston is 7-7.5", then I have to offset the carb to...

Intake arrangement

• FurryOnTheInside
• Sep 11, 2017

"final" intake made from 45° bend fibre reinforced silicone hose and two chopped intake...

 

[Gavin67]

Do you happen to know any offset intakes for 32mm that are good quality? I see a lot of mixed reviews on cheap ones saying that the welds are getting in the way inside the manifold itself or even that there are gaps between welds.