Gutted Cat and Wrapped Pipe

[imagineer]

The bike I got did not have an exhaust heat shield and my son was burning his leg on the header pipe. Thanks to the folks here with the info, I got busy today.

Removed the pipe, scribed an index line and cut it open...



This is what was inside...


Welded back together (poorly)...


A few minutes in the glass bead blast cabinet...


Fresh black VHT paint and header wrap...


Pipe reinstalled with a quickly fabricated heat shield...

[Wild_Alaskan]

nice job

[MICRider]

That looks great! Should solve the hot leg problem . Thank you for posting pics, I always wondered what the cat material looked like in a motorcycle.

[Weldangrind]

Nice work! Remember, you don't have to be a good welder, just a good grinder. When I weld pipe like that, I hide my beads with a flap disc on a 4 1/2" angle grinder. It hides alot of sin.

What was the plug weld for in the cat? Did that hold the cat cylinder inside the tube?

Boy, that cat wasn't restrictive at all... How's the power now? Do you plan to re-jet?

[imagineer]

Originally Posted by Weldangrind

Nice work! Remember, you don't have to be a good welder, just a good grinder. When I weld pipe like that, I hide my beads with a flap disc on a 4 1/2" angle grinder. It hides alot of sin.

What was the plug weld for in the cat? Did that hold the cat cylinder inside the tube?

Boy, that cat wasn't restrictive at all... How's the power now? Do you plan to re-jet?

Since I was wrapping it, I didn't smooth the welds.

I think the plug welds were to hold the cat material. After I welded it, I plugged one end, sprayed soapy water on the welds and blew compressed air in the open end. My new welds were sealed, but two of the 3 existing plug welds were leaking and needed a spot of weld.

I'll have to wait until my son rides it for a report on any additional power. My brief post re-assembly spin was my first ride on it.

I suspect I will have to rejet. It is running too lean and needs almost full choke to go to wide open without sputtering. I haven't looked at the carb yet, are there any mixture screws?

While I had it on the lift, I also cranked up the rear shock to get a little more seat height.

[SpudRider]

You did a very nice job. Thank you for posting the excellent photographs!

Spud

[Weldangrind]

Originally Posted by imagineer

I suspect I will have to rejet. It is running too lean and needs almost full choke to go to wide open without sputtering. I haven't looked at the carb yet, are there any mixture screws?

Yes, there's a mixture screw that trims the air / fuel mixture, but it's for idle and the transition from idle to main. Remove the top cap from the carb, carefully compress the throttle spring with one hand and remove the throttle cable from the slider with the other.

Take the slider assembly to a work surface and remove the spring plate that holds the needle jet in the slider, then remove the needle jet. This is the needle that mates with the main jet, and it is secured by a small circlip in one of five grooves. Move the clip to the bottom groove, and that will max out the fuel flow. Reassemble in reverse order and see how it runs.

If it's still too lean, remove the carb and pull the bowl off of the bottom. The main jet will likely unscrew from a brass hex holder. Keihin and Mikuni style carbs use an intelligent system that references millimetres, rather than some arbitrary number. If the main jet is stamped as 100, that means 1.00mm. A jump to 1.04 mm would be the next logical step.

I pick up jets at my local Yamaha dealer for a couple of dollars each.

[Cal25]

Wow! should not be a problem with heat now.