Suzuki SV650 Riders Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
Good day all. First SV650, first post. Thanks in advance for any and all advice. Thanks also for patience at a long post.

Bike: 2002 SV650

Current issue: The bike starts fine and runs great for ~ 10 minutes at highway speeds (runs great longer if lower RPM, around-town speeds). After about 10 minutes at highway speeds, the bike will start losing power followed by immediatley backfiring hard, and this pattern of power-loss then backfire continues and gets more and more frequent. To me, this PATTERN of backfire behavior seems like a really important symptom. Again, the backfires happen at constant RPMs, not at only acceleration or deceleration. Once the backfires begin, the bike backfires no matter what I'm doing with the throttle.

So, here's the backstory: I bought the bike used, and I should have passed on it. It's obviously been modified to some unknown extent by the an owner previous to the guy I bought it from (he was clueless...I know, I know, lots of warning signs I ignored). The bike had its entire instrument cluster removed at some point in its life, and it has had some obvious mods done: front fork and brakes are from a GSXR, front turn signals removed, rear turn signals replaced, and that's just the obvious stuff.

The beginning problem was this: the bike was not charging the battery. I'd ride for about 10-20 minutes, the bike would start doing the power-loss then backfiring thing, I would limp home, and the next time I'd try to start the bike, the battery was obviously run down (it wouldn't start).

So...

I tested the battery at auto zone and on my own, the battery is fine. Ok, so battery is fine.

I tested for current leaks: there were no current leaks.

I tested the R/R: it was bad! Ok, cool, I read that the Gen1 OEM R/Rs had issues, so, cool, I replaced it with an aftermarket unit (not a MOSFET unit, but one made for the '02 SV650). After I replaced the R/R, all the charging tests at the battery passed muster.

So, I rode it again yesterday, and the backfire issues have continued...however, now the battery isn't run down! Or (MAYBE) it is rundown but not as much. The bike started again this morning no problem, whereas, before replacing the R/R, the battery would have been too run down to start.

I have NOT YET tested that the stator output is healthy: I will be testing that next, but I decided to begin this post first because I am so confused.

So, could it be that the R/R works fine until it gets hot from riding for a while, and then it is unable to send spark to plugs either at all or just not very well? So it begins running strictly off the battery?

Could it be that both the stator and R/R were bad, and I replaced the one but have not yet replaced the other, and so need to do both?

I guess the key symptom I find so important is that the bike starts great and runs great for a set amount of time, then progressively starts the power-loss then backfiring pattern. This makes me think it's not a timing or plugs issue, that's it's an issue caused by the bike's electrical system being forced to run off progressively less power...maybe less power to the fuel pump causing backfires, maybe less power to the plugs causing backfires...

So, thanks for making it this far. I'm too stubborn to give up on the bike. I want to ride her! With your help, perhaps I shall.
 

·
Super Moderator
Joined
·
8,541 Posts
What is voltage at the battery terminals with the engine at 5k rpm? Should see about 14.5v if the charging system is working properly.

If charging voltage is good, double check the electrical connections at the replaced R/R. These connections carry high current and must be high quality.

If the bike is still dying when on the road, try go for a ride with the voltmeter still hooked up, tape it at the handlebars, see if voltage is failing at the same the the engine is dying. Sometimes electrical problems only show up at temperature.

Edit: The replacement R/R for the gen1 SV must be cool running MOSFET type. The R/R is tucked away in the tail and does not get good airflow. Hot running SCR type R/Rs are prone to fail from heat.
 

·
Registered
Joined
·
24 Posts
If voltage is good, back firing after warmed up sounds like a ignition coil braking down, they may test perfect when cold, best to borrow one to try.
 

·
Registered
Joined
·
24 Posts
Reasonable idea, I have found tank vent issues occur quicker with a full tank so knowing this may help rule it in or out.
After filling the tank it often occurs within 1 or 2 kms sometime within 100m
 
1 - 5 of 5 Posts
Top