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FPP small can repair, upgrade on mounting

Started by m in sc, January 24, 2024, 08:47:35 AM

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m in sc

did this yesterday and the day before. for anyone familiar with FPP's, great pipes, but the early ones like to launch the spun aluminum silencers. the aluminum is very soft and the clamp method really just doesnt cut it.

these came up to buy, and i grabbed them. I figured worst case, would put on some tyga silencers but decided to try to save the cans. I'm by NO MEANS a great aluminum welder, and the 2 different grades of aluminum were.. tricky-- to get together especially since the cans were dirty metal.

the sleeve i made is actually a hydraulic filter body (we sell these at work). these are old leftovers from the old cnc machine from work that are sort of everywhere around there

the ID is 1.125", and the narrow part is 25.5mm. I modified them to make stronger ends for the cans, and to thread in some bolts to use for the springs (for a KTM). they are really strong, waiting on the other 2 but it basically doubled the engagement on the stinger. I also shortened the body of the filter by about 52mm.

you cna see one of the can ends was pretty mangled when i got it, i heated it up and straightened it out w a torch and mandrel (socket) before making the new sleeves.

the bolts do NOT act as set screws, but could.
now i need to get the pipes cleaned up and these are bound for the 72 R5.  :toot:


I post waayyy too much



:thumbs: doesn't look like that's going anywhere now
75 Yamaha RD125B   75 Yamaha RD125B (project)
75 Yamaha RD250B   75 Yamaha RD200B (project)
73 Yamaha RD350     77 Yamaha RD400D   79 Yamaha RD400F  
91 Yamaha TZR250R  89 Yamaha FZR400   05 Yamaha FZ6   
05 Yamaha XT225TC  82 Honda MB5  02 Aprilia RS250 Cup (sold)


Nifty! Nice work! Are FPP pipes worth saving? I have a newer set for my RD400. Pipe tore open around the mount and needs welding.
A goal without a plan is just a wish.   ~ Antoine de Saint ExupĂ©ry

m in sc

IMHO, yes hey are very close in performance on a stock-ish motor to tapered head pipe specII's



Uh oh...
These have survived on two different RDs for the last 40 years or so.
However, I might have to get creative.

m in sc

ive launched them, and also ride my bikes almost every day. (well not this time of year). i mean, FPP changed the design themselves... there was a reason.


Cool project. Be sure to post the final product. I love seeing things come back to life.


Quote from: m in sc on January 24, 2024, 12:35:33 PMIMHO, yes hey are very close in performance on a stock-ish motor to tapered head pipe specII's

Sounds great! You definitely made an improvement to the stock silencer mount (understatement...)
I have some questions though:
Are the stingers as short as the visible part, or do they extend into the chambers?
And, did Spec 2 pipes come with both straight and tapered headers? If so, was that the only difference between them? And how much difference would tapered vs straight headers make?

m in sc

as far as the pipes/stingers, they were about 2~2.25" long total, ID of 23.5mm. they did NOT go into the belly of the pipe. the stinger went into the can a bit over 1" and the can + stinger length (also with an ID of 23.5mm), total, is about 15"~15.25".

yes, specII pipes came with both straight, early, then later tapered head pipes. I've run both, the tapered headpipes def improves midrange transfer, the 'hit' isn't as abrupt. i havent measured them pipe to pipe but otherwise, i think thats the only main difference


Did you get the dents out of the silencers?

m in sc

nope not yet.. might not.. but will try. torch and a mandrel and a light hammer


Mark I have two new unmolested FPP silencer canisters if needed. CHEAP.