ANY QUESTION ANSWERED How do I get the most from an aftermarket exhaust?
If we don’t know the answer, we’ll find the person who does
I’ve had my 2012 Yamaha R1 for a while and I’ve saved enough pennies to fit a £2500 Akrapovic Evolution full-system. What other components or work do I need? Guy Alcock, Crewe
Answered by Tony Scott, T3 Racing A manufacturer’s fuelling map tends to make the bike lean low down to pass the emissions regs, and rich at the top to keep the engine cool.
If you just fit the pipe and do nothing else the bike will sound good, but it will have a snatchy throttle response, and most engines tend to run even leaner at the bottom-end if they have a freerflowing pipe. You’ll have trouble starting and pulling away from lights and it will get hot in traffic, pushing past 85 degrees, which saps power. Between 7000 and 10,000rpm it will feel OK, but then it’ll get really heavy on fuel at the top-end – as low as 18mpg.
The fuelling maps in the ECUS of Italian bikes, KTMS and pre2012 Triumphs are tuneable, but Japanese kit is locked down tight, so you’ll need an external fuelling module such as a Power Commander. Finally, budget for £200-300 setting it up on a dyno.
Tempting as it may be to exchange maps online with other riders, a good dyno operator will check the base fuelling through the rev range at 5% throttle intervals in every gear. Not only will that give you up to 15bhp more, but it won’t pop and bang on a closed throttle and it will pull cleanly too.
I’m looking to replace the rear tyre on my Honda 125 Forza scooter. I do about 6500 commuting miles each year, in a mix of dual-carriageway and urban town work. Stuart Allen, email
Answered by Bryn Phillips, Cambrian Tyres There are many good choices for the Honda 125 Forza these days in the 120/70-15 and 140/70-14 sizes which feature on lots of scooters. Bridgestone’s new Battlax SC is proving very popular with a good balance of performance, durability and price. Continental’s long-serving Contitwist and Dunlop’s Scootsmart have similar performance to the Bridgestones. The only tyre that I can think of that might give better durability than those three would be Michelin’s City Grip.
If you are going to shell out on a full system, don’t skrimp on dyno time