So I found this thread which possibly explains what’s going on with my exhaust (2nd post particularly relevant).
i think this may be about gas velocity, which would sorta explain the current counter-intuitive performance improvement by adding the baffle in the can. I’ve also realised that it might be better still if i take the forward baffle out (the one which came with the exhaust system) and only have the rear one…that way i might get better performance still and regain some of the nice sound.
It may also do nothing/make it slower in which case it’s going back how it was….gonna find out today hopefully.Continue reading Baffled – Part 3
I did another quick run across town just now with the baffle in and it definitely seems quicker. I dunno if that’s because I’m less conscious of the rpm and so ride differently but it definitely felt like it wanted to *go* again. Much grinning when I got home.
I guess it’s possible that at low/mid rpm the little bit of restriction might improve torque somehow – I guess there’s sound waves and stuff going on in there to some extent like a 2-stroke. I didn’t really get chance to go flat out though and that’s where I’d expect the baffle to be a restriction…will have to see. Didn’t seem to be a problem revving high at speeds up to 50ish though, kept finding i had to back off a bit.
I’m still not loving the sound but stealth is better and obviously whatever’s quicker wins. Interested to see how it does on a test run. I guess I need to figure out some sort of timing malarkey I can work with gloves on first, though even just seeing how it performs when flat out with the baffle would be interesting. Next time she’s on the dyno I guess we’ll find out for sure but that won’t be for a while yet.
I did a little test run today, primarily wanting to put some miles on the new tyres…unexpected results in other areas tho.
A couple of months ago when I got the PCV fitted and bike tuned I also got them to put a 15t sprocket on the front since I’d kept bouncing off the gearing up until then and was looking for better cruising rpm (e.g. so I can cruise at 70ish over longer distances without revving like a twat the whole way). which is fine, but it meant I’d never had a direct comparison with before/after tune on the original gearing.
In the spirit of seeing just how good my “mud and snow” rated winter tyres are, I’m wanting to do some “local exploring” where I’d likely be wanting acceleration over top end so I put the 14t back on to test. Also for exploring a degree of stealth may be beneficial so I put the baffle in the end of the can (which I’ve also never tested properly). Without the baffle “stealthy” is definitely not a quality it has.Continue reading Baffled!
So given the bike is my main transport now and with a cold winter promised I figured perhaps prepare a little bit.Continue reading Winter tyres for the YZF-R125
Not really sure where to start to I guess start at the beginning and will work up to date from there…
I’ve been into messing with cars for years, mostly mk2 golfs but only got into bikes sorta by accident when I fell in love with stretched scooters (they’re ridiculous, I know). Somehow along the way I got the idea that I’d quite like to do the blood bikers thing and realised that i’d need a geared bike to get a proper license in order to do so… So after some online research, concluded R125 was the way to go. A friend happened to have one sat in his garage (see pic above, as I found her he’d since got a blade and was bored with the 125) so I did my CBT and here we are…Continue reading White ’08 Yamaha YZF R125
Here are a few pics from recent progress…
I’ve been working on trying to get it as “together” as possible, all trim, bodywork and stuff, before putting the floor bars on to get the best idea of how to do them. I think now I know what I’m supposed to be doing and now just have to actually get them in. Hopefully I’ll get into that this week, weather permitting.
The back rides up when there’s no weight on it which makes it look a little odd, but when you’re on it, it all lays flat and lines up right.
The last pic is with me sat on it as you can hopefully see then both the rear mudguard and the exhaust come into alignment. It’s very, very long for a scooter but looks to be headed the sort of direction I was hoping (japanese “big scooter” style).
Unfortunately this ran into running problems and I decided to sell it and got my Audi back on the road instead – which is already turbo and much faster 😉 ah well. priorities init.
For anyone looking into doing this I think what I had planned for the polo *was* totally feasible.
Since you can’t adjust the fuelling in the ecu on the 6N polo, my plan was to add a smallish turbo (I had a pair from an Audi RS4 (2.7L divided by 2 = 1.35..which ought to be about right for the polo).
Then have a secondary injector which is activated by a boost switch and dumps a load of fuel into the inlet tract. When no boost it runs on the stock fuelling, and as soon as there’s boost it douses it. It wouldn’t be sophisticated but it hopefully wouldn’t melt.
Downsides are that this will be pretty imprecise – like you won’t get ideal fuel distribution per cylinder so changes are some will run hotter than others, which may lead to meltage if pushed too hard. I guess it would be similar to adding a wet nitrous system, with similar issues.
I was only looking for around 5psi of boost which I reckon the stock motor could probably take all day long. My hope was the anti-knock sensor would adjust the timing automatically if it got a bit too excitable.
Any more than 5psi and you’d probably want to be looking into better fuelling control, reducing the compression via thicker head gaskets (e.g. copper, which are available on ebay), and would perhaps need something a bit more sophisticated than the knock sensor to retard the timing.
Obviously the costs start to go up pretty steeply at that point hence sticking with 5psi….except it beat me to it and it started having starting problems we couldn’t fathom and I needed a working car for work so i cut my losses and got the audi back on the road. It’s something I may come back to in future though the syncro is my priority.
Ah well.. I’ve got a big box of turbo bits for sale if anyone needs them (2x RS4 turbos, some of the original manifold pipework to rob flanges from etc, boost sensor, boost gauge, injector etc.
…unless..maybe…the turbo might go on the syncro. hmm. Turbo might be a bit small for the KR motor but again, only needs to make 5psi-ish. At least with the syncro the injection is mechanical so can be adjusted, and the timing is probably simple enough to fiddle too, plus I have a couple of spare motors.
Also it would *massively* simplify the downpipe situation on the syncro which is a problem I will be facing anyway if I can’t get the current downpipe to seal properly.
hmm…let’s see what happens.
Now that the rear suspension is sorted I was able to figure out the positioning of the exhaust. Obviously with adding offset and the wider wheel the exhaust needed a little bit of “editing” to clear the wheel. Was a bit nervous about messing this up but it actually went ok.
So the air ride sorta worked but I wasn’t happy with the reliability, and that’s not something I’d want to fail at speed.It was holding up the rest of the project so I decided to go with a regular shock on the back for the time being and come back to the air later.