What was I thinking!…
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Tzr125RR tailpipe…
Man this thing is heavy! as well as looking like it was used as a bobsleigh!
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WTF is that inside?! Someone left a WW2 torpedo inside!…
Is this normal or was this an asthmatic example of Yamahas finest? This ‘can’ weights about a kilo, no shit!…
It’s weird cause the expansion chamber breathes really well with no obstructions, though it ways a Shit ton as well!!…
This was not an easy picture to take, that spot of light is the only ‘free airway’ through the can! It was only visible if I angled it’just so’…
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I seriously can’t believe that a tailpipe would be so restricted!
This is what came out:
This is what any exhaust gas faces when exiting the expansion chamber:
I’ve got a Big1 tailpipe I’m going to try and fit to the expansion chamber. I ran a clutch cable outer through it just to make sure it wasn’t severely baffled as well! TF it’s clear!…
Are Dtr tailpipes like this? They’re definitely heavy enough!…
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@SpookDog Stock DTR tailpipes are like your TZR-R tailpipe; you can't see through them at all. I've never considered the stock DTR tailpipe to be a restriction, all mine with stock exhausts have revved to 10,000rpm+.
I did however once bolt a brand new DEP silencer on to the stock front pipe on my '93 3NC, and the bike immediately refused to rev any higher than 9,000rpm. I tried it in several different directions to rule out headwinds etc. and it just would not rev out fully. Refitting the stock tailpipe cured this straight away.
Your front pipe looks very similar in construction to a stock DTR front pipe as well so until you've rebuilt and run in the engine and properly assessed its performance, I'd resist the temptation to do anything irreversible to the exhaust.
Lots of people "gut out" the stock DTR front pipe in the mistaken belief it will liberate a ton of extra horsepower but it often makes it slower. The DT125R/DT200R styling was based on the 1988 YZ250 and the expansion chamber is about the same physical size. Within that there was enough space for an appropriately-sized, functioning expansion chamber for a 125cc road/trail bike and enough noise suppression material for the bike to pass a noise test (whereas the YZ is for closed-course competition which is why it has a single-skin racing exhaust). If you chop it open with an angle grinder and rip all that stuff out, it will not only sound like a wasp in a tin can but also you’ll probably lose power as you no longer have an expansion chamber which matches the porting/carb/crankcase volume etc. By all means bolt on an aftermarket silencer and try it but from your pics, I'd be surprised if the stock silencer is restrictive. Probably more likely it's like that to manipulate sound waves to pass a noise test so the owner doesn't have to suffer the hassle of repacking the silencer periodically.
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I dunno bud. I thought that the pressure pulse/wave was all done in the expansion chamber? I know SFA about 2T exhausts though, only the very little I’ve read online. It’s moot for me anyway. The doodle-bug bit is supposed to be welded into the end can. It’s basically fallen apart 🫤
Big 1 or bust! Saying that I do have an aluminium giannelli kicking around somewhere …
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@SpookDog Yes the expansion chamber does the lion's share of controlling the pressure waves but the end can plays a part as well, and they need to be matched to one another. And road-going two-strokes are something of a special case; making an engine deliver the addictive two-stroke sound/power delivery and making it quiet enough to be acceptable to the general public is a tall order compared to just punching out a production run of YZs for the track. I used to wonder how manufacturers could afford to redesign MX bikes every year but in truth you don't even get a warranty of any value when you buy a brand new one, let alone having to pass an MOT or noise test and this is where a lot of the R&D money goes on road bikes.
RGV250 standard cans weigh a ton and are silenced in the same way as your TZR can and a good stock one of those is good for 60bhp/130mph. Once on a summer's evening I was greenlaning up at Pepperbox Hill when I hadn't had my 3NC for very long, I slowly passed this family with young children and met up with them a bit later when I stopped, and they commented they thought I was riding an electric motorcycle when they saw me coming towards them! 5 minutes later Greta (use your imagination) and myself were doing 70mph on the dual carriageway towards Salisbury with a bit in reserve.
In truth I don't really know one way or the other, but testing both setups back to back should prove interesting
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Seeing as the original tailpipe is busted I decided to use some of it to make another.
I cut the threaded ring off of the bit that was snapped off from the inside of the original.
Then I cut the excess jointing pipe off of the big1 tail pipe.
So I could join it to the big1 tailpipe.
I drilled holes in the big1 to match.
Then used Allen bolts to join them.
The idea being it ‘locks’ the Allen bolts in place and lets me use the joining gasket from the original. So I can remove the big1 tailpipe without having to dismantle it to get to the Allen bolts heads, if/when I want to remove it. I just have to undo 3 10mm nuts.
End product:
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I do hear what you’re saying. I swapped the standard & big1 tailpipes around on my dtr a few times, for MOT and because my expansion chamber was a big1 as well. It never made any noticeable difference to the ride~feel or power. It was just the standard can was so stealthy! I’m 53 years old and am not into noisy pipes in any way at all!
I just assumed that it was a restriction because I’ve never seen the like before. Hindsight makes me realise it’s made that way because it’s a non serviceable part made to last forever. I love the build quality and finish of the front/expansion chamber as well! Double skinned, stove enamelled. Over engineered goodness! That front pipe is 30 years old!!… -
Cheers guys! I only hope that it works
The big1 is like any other aftermarket one, it has nothing but a pierced hole tube with fibre wadding. I’ve got the carb and air box fitted. I just need to add the loom and a battery to fire it up. Monies are tight though, I’ve gotten my tax & mot & insurance all due this month 🤪 …I do have the rubber repair kits for the front brake master & calliper to be getting on with.
I’ve stripped the rear calliper without breaking anything, just need to order repair kits for it and the 13mm Brembo master that it uses…Wish me luck, please!…
One step closer…
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Found out that the FZ600R uses the same Sumitomo callipers as mine. There’s a pair of them on fleabay for £65, in excellent condition with pads! I wish it was one of the times that I had monies!!
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I would love to put twin discs on this!… -
Actually they are similar, not identical!
One thing I really am not keen on is the big fat 250 ass on this bike. It looks kinda stupid with the 150 tyre under it. I want to find a nice slimline single seat pod to fit to it. Any input appreciated…
I’m thinking 1980’s gsxr slab side kinda thing…
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Re: the see saw linkage. I read somewhere that it’s for during overrun, when the revs are above 6-7k but the throttle is closed. It kinda makes sense as it’s activated by the power valve servo? What you recon?…
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@SpookDog Yes I think that's one of the aims of having the see-saw linkage, to avoid the motocrosser-seizing-at-the-end-of-the-main-straight-at-a-beach-race scenario. I guess the TZR125R in its natural habitat could benefit more from this than a DTR because if you took it on a track day somewhere, you'd spend a fair bit of time per lap braking for corners whilst keeping the revs up to get on the power mid-corner and on the exit.
From memory I think the RGV250 had a similar system but don't quote me on this. The fact the TZR250 parallel twin had this and the 350YPVS didn't is IMO a factor in the TZR250 being able to reliably do everything the 350 'valve could do with 100cc less.
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@SpookDog said in What was I thinking!…:
If anyone can tell me what the 170 Athena revs out to, please do!
If memory serves well,I saw about 13000 rpm/5th gear,136km/h on the road when it was running good last time,run out of road for the 6th gear.
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@SpookDog My 3MB ran very well on this stuff, equal spec (JASO FD is the Japanese industry standard for racing two-stroke oil) to all the brand-named oils and I've known MX/Enduro guys to run it in modern KTMs etc with no issues:
Very good ebay seller generally, they have similar deals on grease and stuff
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Cheers bud, looks good. Any issues with sticky power valves? I bought some cheap synthetic 2T that was fine except for it making the power valve gum/stick-y
