Author Topic: Not another bloody SR250?  (Read 5658 times)

Offline zap2504

  • Posts: 363
Re: Not another bloody SR250?
« Reply #30 on: Oct 15, 2017, 19:18:51 »
Excellent job! Now we want to hear about some ride reports. Do the engine/suspension/seat mods work as well as expected?

Offline ManxKat

  • Posts: 26
  • Older but no wiser
Re: Not another bloody SR250?
« Reply #31 on: Oct 19, 2017, 10:17:04 »
Settle down boys and gurls, it's tech time!

OK, there's now about 100 miles on the Yam since it was completed and I'm pleasantly surprised by how well it's all come together. The ride is on the firm side but that's my preference - the shortened forks are now running the stock capacity of 10 wt oil and they cope really well with everything the crappy Manx roads can throw at them. The riding position does encourage a bit of a slouch but it's not uncomfortable. Oh, and having a disc up front rather than a weedy single sided drum makes stopping a much more relaxed affair.

More importantly, an afternoon at the dyno has yielded some very interesting results Ė the attached printout shows the final outcome (the previous run is also on the graph, itís the one in blue).
Using a Jadus intake kit with a 120 Main jet, 50 Pilot jet, stock downpipe and a silencer that's probably as restrictive as the stock item it's created a whole different feel to the bike from about 5,500 to 7,000 rpm and, at 6,500 rpm, thereís a genuine 15% power hike (from 14 bhp to 16 bhp) which just it makes it so much easier to ride. Iím never going to be troubling R1s but I now can hold gears rather than jump up and down the box to keep a constant speed up hills. I'm still playing with the needle position but the stock setting seems to work best for slow speeds around town.

My dyno guru reckoned that with a less restrictive downpipe and/ or silencer a 115 Main jet would work well and see the mid-range power increase carry on to the red line.
With a 17/ 43 sprocket set up the theoretical top speed is now 84.6 mph but I doubt Iíll get anywhere near that given it (together with me board) makes a house brick look aerodynamic!

The only issue was that all my cheapo, made in China LED idiot lights failed within five miles. Who would have thought that £1.25 items (with free postage no less) might not have been top quality? Sturdier items have been ordered.

So that's it, project successfully completed, thanks for checking it out.

« Last Edit: Oct 20, 2017, 04:58:36 by ManxKat »
The difference between knowing your sh*t and knowing you're sh*t