Replacing header pipes on 4LO spanies

[LC Cnd]

Was able to purchase a set of '81 exhaust pipes luckily but found the pipe(s) leading to the heads rusty and heavily pitted on the inside curve(s). Noted that even with a good clean and powder coating the pitting will will show. That said, I thought of replacing those sections with new automotive soft steel aluminized exhaust stock 14-16 gauge and I have access to a pipe bender. My concern is the gauge might not handle the 1600 F heat at the head. The original pipes appear thicker gauge even without the '81 head flange. Recommendation?

[JonW]

you might be able to buy some used ones cut off some pipes too crushed from crashes?

[LC Cnd]

Jon all I could locate was a right one 2/3'ds road rash for $100. I can get 2 new pipes for $40 properly bent if they will stand the heat.

[yam4l0]

I've got a pair you can have, just pay the post.

[Bare]

NO issue with the heat at the head for Auto type pipes Although Ali sprayed pipes are a sketchy materials choice.. Midas Muffler stuff.
One can readily Buy bent mandrel bent exhaust tubes from most Auto parts shops... this WILL take Any heat from the lil 2 stroke noise maker
Expansion chambers 'worth owning' have a divergent (progressively bigger) header pipe .. Are you talking about oem Mufflers then?

[LC Cnd]

Yep - OEM pipes. The reason I'm going with the aluminized 14 gauge stock mentioned is it is what is used for the pipe bending machine - that is what I was told. I will ck on the bent mandrel tubes - good tip and see how it goes.

[LC Cnd]

Thx for the offer Nigel. Your generousity will be plan b if the current one tanks. Hope to find that out after the holiday weekend - happy Easter each and every one.

[LC Cnd]

Bent the pipe. Next is to lathe/drill out the new head brackets. I'm receiving some info, hopefully next week, regarding factory tech tips (3 total appearently) Yamaha dealers received to modify the interior of the pipes to obtain a couple more hp. Should be interesting.

[yam4l0]

I'm receiving some info, hopefully next week, regarding factory tech tips (3 total appearently) Yamaha dealers received to modify the interior of the pipes to obtain a couple more hp. Should be interesting.

This maybe?

[RuZty]

I would not use standard muffler tubing as you show above. Proper mandrel bent tube has a constant ID vs. the necked down tubing you have. I would definitely go with the kind offer from yam4l0 and do it right. If you carefully cut the pipe and the header back to the factory weld you should find fitting them a lot easier too.

[LC Cnd]

What's interesting is the stock pipe head curature has the same inside bend crush as the new ones. I went to a local Lordco, looking at mandrel piping (b4 making new ones) and did not note any difference in what's in the photo other than the crush was not present. All aluminized mild steel at Lordco. I am going to a gent who builds auto racing exhaust, this comming week, for a 2nd opinion. Cheers for the insight. Nigel the technical service bulletin appearently does have the same advise as yours. I recall him stating the bulletin recommended removal of the wire mesh/net used to baffle and 2 other mods. He state he save the bulletin circa 1982 and the net removal gave the stock pipes the same crackle as Microns. I recall Niall McKenzie, during the 2015 PROAM race had removed the nets to the chagrin of his competitors. I'll be hopefully looking at TSB this week and take a pic, of it, if located.

[LC Cnd]

Ck'd with the auto exhaust racing gent and he advised it will work - not as long lasting but will suffice. Got some blanks cut for the flange brackets to have milled next.

[LC Cnd]

Got the brackets complete. Now its time to rebuild the pipes.

[Bare]

Interesting Tech bulletin. Frankly IMO it's the removing of the step in the cyl head casting (and presumably using something 1/3 rd the thickness as a Head Gasket)
and the raising of the ex ports that gave 98% of the 'improvement"
Oem pipes were crap, by even a charitable view. Heavy as pig iron and over restrictive.
Big job ahead of you I'm thinking.

[JonW]

Not crap actually. While USA OEM cat pipes used on the RZ are iffy, the (ROW) OEM pipes for Lc and RZ actually have been proven to make good power, they are heavy tho.