Hi All, just had my brand new vfr 800 for a week, I fueled up this morning then on the way home this afternoon I noticed a noise that would happen if I rev the engine very slowly up to 100rpm, then the revs would drop about 100-200 rpm. If I give the engine a gut full of throttle it was fine. The noise is kind if like a soft thud as though it is a little backfire. I rode it home about 40km's of mostly highway work then stopped at some shops and it was still doing it. Rode it straight to a near by honda dealer but then of course the noise stopped, great timing! Talking to the mechanic, he said it would probably be the fuel injection pumping too much fuel at that low rev and I should be more vigorous with the throttle. I told him I never had this issue with my 97' vfr 750 in which he replied because the 750 was not injected (which is correct). It could be bad fuel even though I only use premium, but was wondering if anyone else experienced this? Is what the machanic said viable (he seemed to know what he was talking about)? If it happens again, should I take it to the dealer? Thanks.
Mine backfires some alittle on decel that is very audible now with the aftermarket pipe, but I could faintly hear it with the stock exhaust as well. Its likely a little bit of backfiring caused by the pair (pulse air injection reduction) system. The pair system injects fresh air into the exhaust right as it leaves the cylinders to help burn off any unburned hydrocarbons. They are notorious for causing some backfiring through the exhaust, and not just on motorcycles. Its nothing to be overly concerned about, unless the bike begins to run poorly(system is leaking exhaust back into the air box) or the bike begins to backfire very loudly. Most guys on here block off the system, which I will be doing this winter to my 99. It will reduce the backfires and eliminate the possibility of the pair valves getting clogged with carbon and not sealing off when they should. This allows exhaust gases to travel back through the system into the air box, causing the engine to ingest exhaust gases. Hope this cleared a little bit of it up for you.
