Q: I ran across CMM in a forum and like a parent with a poorly child I turn to you in hopes of saving my nearly-new bike. Don’t ignore me just as it’s ‘new’. I planned some mods to my Raider: Cobra Dragsters exhaust pipes with Big City Thunder ‘monster baffles’ and I installed a K&N air filter to replace the stock and I have a Cobra F12000 PowerPro fuel management controller. I had a professional mechanic install the stuff and it now pops so loud on deceleration that it’s embarrassing to ride.
The shop blames the PowerPro product and the PowerPro folks blame the shop for faulty install (air leaks, although they have no evidence of that and the shop says it’s vacuum tested). The shop wants me to take out what seems like a second mortgage in order to pay additional money to it to start dissecting the engine to figure out what’s wrong. After asking around people seem to think it could be one of three things.
Firstly, an exhaust air leak. But it’s had new crushed rings and the pipes are one piece. The shop says it tested for leaks. Secondly, not enough back pressure in pipes. My response: these pipes are rather short but have been used by thousands of folks without this as a known problem, plus I’ve used Big City Thunder ‘monster baffles’ before and they worked great (albeit on a different bike with different pipes). Finally, it needs more fuel thus an ineffective fuel control device doesn’t allow dialing in at precise points. My response: people seem to have success with this unit and some say it actually eliminates popping, granted, maybe not with my exact component mix. What do you think the problem is? Help!
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A: The exhaust popping is often found on big twins with free-flowing exhausts and the usual answer is to allow a bit more fuel into the engine and you have addressed this by fitting the PowerPro unit. This is supposed to ‘autotune’ but evidently that is not working perfectly. Firstly, do not pay any more to the shop for it to take everything to bits: is Cobra saying that the popping never occurs on the Raider after those products have been fitted? Is it willing to accept that there may be a fault in one of the components? Maybe a Raider forum might have some other owners who have had similar problems?Enjoy more Classic Motorcycle Mechanics reading in the monthly magazine. Click here to subscribe.