Anyone have any possible ideas on what could cause my bike to backfire all of a sudden? Never had this trouble before, but now everytime I downshift hard it sounds like the freakin Fourth of July. I did run a tank of 87 octane through it a couple of weeks ago (the station was out of 93 and so was I - not many options their) which is around the time the backfiring started. I have been through 2 tanks of 93 since then. Any input would be appreciated, I am not much of a mechanic. 06 S2R 800 with Termi system if that is relavent. Thx.
Quote from: psycledelic on August 26, 2008, 05:00:30 AM
Anyone have any possible ideas on what could cause my bike to backfire all of a sudden? Never had this trouble before, but now everytime I downshift hard it sounds like the freakin Fourth of July. I did run a tank of 87 octane through it a couple of weeks ago (the station was out of 93 and so was I - not many options their) which is around the time the backfiring started. I have been through 2 tanks of 93 since then. Any input would be appreciated, I am not much of a mechanic. 06 S2R 800 with Termi system if that is relavent. Thx.
Check all the joints in the exhaust.
I believe you've developed a leak.
Quote from: ducpainter on August 26, 2008, 05:13:36 AM
Check all the joints in the exhaust.
I believe you've developed a leak.
I 2nd this theory.
Popping on downshifts is a common symptom of an exhaust leak. I had the same think occur on my 620 w/ high mounts. The S pipe got a little loose and *POP pop poppop* started. 5 min to looks things over and tighten the connections and it was gone.
Quote from: psycledelic on August 26, 2008, 05:00:30 AM
Anyone have any possible ideas on what could cause my bike to backfire all of a sudden? Never had this trouble before, but now everytime I downshift hard it sounds like the freakin Fourth of July. I did run a tank of 87 octane through it a couple of weeks ago (the station was out of 93 and so was I - not many options their) which is around the time the backfiring started. I have been through 2 tanks of 93 since then. Any input would be appreciated, I am not much of a mechanic. 06 S2R 800 with Termi system if that is relavent. Thx.
Most people have found that the 2 valve motors actually run better on 87
Quote from: ducpainter on August 26, 2008, 05:13:36 AM
Check all the joints in the exhaust.
I believe you've developed a leak.
Would this be the same diagnosis if back firing only happens during certain conditions? i.e. I did a lot of hard canyon riding this past wknd and my bike began to back fire pretty regularly on deceleration into corners. Bike is a 620 with Spark high mounts and it was a hot day. Oil temp reading in the high 270s and I was keeping the revs in the 6-8K range. On more everyday type of riding I
might hear it back fire once in a blue moon, but pretty much never. Revs usually stay around 4-6K when I'm just cruising around.
I'll make sure to re-check the connections to the header when I get home, but just wondering if my back firing issue could be something else...
thx,
b.
Quote from: b. on August 26, 2008, 11:03:41 AM
Would this be the same diagnosis if back firing only happens during certain conditions? i.e. I did a lot of hard canyon riding this past wknd and my bike began to back fire pretty regularly on deceleration into corners. Bike is a 620 with Spark high mounts and it was a hot day. Oil temp reading in the high 270s and I was keeping the revs in the 6-8K range. On more everyday type of riding I might hear it back fire once in a blue moon, but pretty much never. Revs usually stay around 4-6K when I'm just cruising around.
I'll make sure to re-check the connections to the header when I get home, but just wondering if my back firing issue could be something else...
thx,
b.
This might be a combo thing - your fueling could be a tad rich in the higher RPMs so you're getting some unburnt fuel into the exhaust. A little more gasoline + oxygen from a leak resulting in an afterburn popping. At the lower rmps somethings a bit different, so you don't get as much afterburn... Just some speculations on my part. But either way, can't hurt to chekc your exhaust connections
check the intake as well. I had one of the vacume screws drop out at a track day and it would backfire backing off.
Cool, I will check my exhaust out in the morning. Glad I posted cause that wasn't even on my radar of possible problems. Thx everyone for the help.
If the exhaust leak doesn't bear you any results, I'd def check in on your air/fuel ratios. What kind of weather are you riding in to get 270 degrees out of a 620?? I've romped on my S2R 800 in 95 degree heat and not even hit 240. I don't know that much about air/fuel mixtures, but isn't excessive engine heat a possible result of running lean? I know that sounds counter intuitive, but IIRC that's what my ex-mechanic dad mentioned.
Quote from: Jarvicious on August 31, 2008, 11:22:03 AM
If the exhaust leak doesn't bear you any results, I'd def check in on your air/fuel ratios. What kind of weather are you riding in to get 270 degrees out of a 620?? I've romped on my S2R 800 in 95 degree heat and not even hit 240. I don't know that much about air/fuel mixtures, but isn't excessive engine heat a possible result of running lean? I know that sounds counter intuitive, but IIRC that's what my ex-mechanic dad mentioned.
Your S2R has an oil cooler. My 620 doesn't. For my own peace of mind I might invest in one, but it's a pricey addition. :-\
Quote from: b. on August 31, 2008, 03:44:57 PM
Your S2R has an oil cooler. My 620 doesn't. For my own peace of mind I might invest in one, but it's a pricey addition. :-\
This I did not know :) Thanks for the schooling.