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Discussion Starter · #1 ·
I have been working on my bike that I was given but it sat for years. (2002 Suzuki SV650S)

Currently having an issue I am thinking might be exhaust. Figured I would see if anyone can chime in...

Here's what has been done...

Carbs rebuilt
Bad hoses replaced
New air filter
New spark plugs
New fuel pump
New petcock

Right now I have an intermittent issue where it will start making a deep popping sound and backfire under throttle ( video IMG_4742.MOV ).

Keep hearing that it must be running lean.

I noticed that the header pipe had black fluid coming out ( pic IMG_4743.HEIC ). So Loosened and wiggled a bit, then retightened and that seemed to help but only temporarily. That also got rid of the ticking sound which I hear was air coming out of the header.

I also noticed I have the same thing happening on other areas of the exhaust joints (pic IMG_5160.HEIC ) and can even wiggle the pipes and they move at the joints ( video IMG_5175.MOV ).

Question is, does it seem like that would cause the issue? Going to be taking it all apart and putting new gaskets and resealing all the joints as well as cleaning them up.

Rode last night for about 30 minutes with a stop in between and it was fine, then stopped again and when I started it back up it was doing that. Had to coast it home.

Anyway, any help would be awesome! Really hoping after redoing the gaskets and all joints it solves it.
 

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sounds like its only running on one cylinder. maybe let it run a few minutes and see if the other cylinder tries to kick in.possible choke issue.
 

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Discussion Starter · #3 ·
sounds like its only running on one cylinder. maybe let it run a few minutes and see if the other cylinder tries to kick in.possible choke issue.
Definitely lean, but with newly cleaned carbs and new plugs, etc. Wondering if the exhaust joints being so loose can cause it.
 

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popping from exhaust would have a minimal effect. sounds like as the rpms increase the missing cylinder tries to ignite. the pop and flash was fuel igniting in the exhaust.let it run for three minutes gently raising and lowering the rpm up to approx. 3,000 rpms. check the choke cable is functioning.
 

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Discussion Starter · #5 ·
popping from exhaust would have a minimal effect. sounds like as the rpms increase the missing cylinder tries to ignite. the pop and flash was fuel igniting in the exhaust.let it run for three minutes gently raising and lowering the rpm up to approx. 3,000 rpms. check the choke cable is functioning.
A little more history on it...

When we did the plugs and put the carbs back in, bike ran fine. Did a quick test drive and no issues.
2 days later rode it for a bit, maybe 7-10 miles or so, no issues.
3 days later went to go out on it, and that is what the video is from.
Someone said to loosen the front header and move it in and out a bit then retighten, did that, ran fine that day.
Rode it again another day and all ran well, it did occasionally make that deep sound on the ride but only a few times and nothing else.
Last night, rode to a store and was fine. Went to another store and was fine. After that stop, it started doing it nonstop the rest of the night. Haven't tried it since but will take a look again tomorrow.Today I figured I would mess with the pipes to see if they were loose and saw how much was.

Needless to say it has been fun getting this bike back up and running lol
 

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Exhaust leaks can cause popping. I would get some Seafoam/Fuel cleaner or similar and put some in the Gas and give it a blast and see if it improves but check for the leaks in the exhaust and the Air Filter to Carb seals.

When I fitted a Slip-On can on my 99 I used stuff similar to this on the joints to make,"Gas-Tight",





Cheap,"Chinaprovich" Slip-on.
 
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Discussion Starter · #7 ·
Exhaust leaks can cause popping. I would get some Seafoam/Fuel cleaner or similar and put some in the Gas and give it a blast and see if it improves but check for the leaks in the exhaust and the Air Filter to Carb seals.

When I fitted a Slip-On can on my 99 I used stuff similar to this on the joints to make,"Gas-Tight",





Cheap,"Chinaprovich" Slip-on.

Even with newly cleaned carbs and new plugs?

I did put some Marvel Mystery Oil in at first, I use that in my truck and read it can be good for the bike occasionally just to keep things lubricated.

Never used Sea Foam before.

The weird thing is unless it is always running on one cylinder it is hard to believe that is the issue. Cause it will run fine then suddenly start doing that deep popping and when it does it loses power.

The exhaust is definitely leaking, can hear it and see it. Gaskets have to be done, and I have to seal the joints. Looking at whether I should just replace the system.
 

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An exhaust leak near the cylinder could cause popping and can also cause valve damage, sucking in cool air. Did you disassemble the carbs to clean? They symptoms you have described can be from dirty pilot jets and semi-clogged passages in the carburetors. At minimum remove the pilot jets, spray carb cleaner through the jets followed by air. Different forums seem to have favorites when it comes to carb cleaning in a can, Seafoam is popular along with Berryman's, Chevron Techron, and Mechanic in a bottle. Make sure you have a good seal with the exhaust where it meets the head, can't believe air leaks downstream from that would be causing the popping or lean condition you describe. Idle runs on the pilot jet as you move up in the RPM range the needle & main jet come into play. Does it have a jet kit? if you're running an aftermarket header it would benefit from a jet kit, including a needle change. A jet kit will have grooves at the top of the needle, have you tried new clip positions? Raising the clip to a higher groove on the needle will lean the mixture and richen as you lower the clip.
 

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Even with newly cleaned carbs and new plugs?

I did put some Marvel Mystery Oil in at first, I use that in my truck and read it can be good for the bike occasionally just to keep things lubricated.

Never used Sea Foam before.

The weird thing is unless it is always running on one cylinder it is hard to believe that is the issue. Cause it will run fine then suddenly start doing that deep popping and when it does it loses power.

The exhaust is definitely leaking, can hear it and see it. Gaskets have to be done, and I have to seal the joints. Looking at whether I should just replace the system.
You know the exhaust is leaking, and you know the exhaust is popping. Fix the leaks and see if that fixes the popping.
You could have a misfire but I wouldn't jump to that conclusion. Fuel additives are not a solution to this problem. They won't hurt it, but they won't fix exhaust leaks.
 

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Discussion Starter · #11 ·
An exhaust leak near the cylinder could cause popping and can also cause valve damage, sucking in cool air. Did you disassemble the carbs to clean? They symptoms you have described can be from dirty pilot jets and semi-clogged passages in the carburetors. At minimum remove the pilot jets, spray carb cleaner through the jets followed by air. Different forums seem to have favorites when it comes to carb cleaning in a can, Seafoam is popular along with Berryman's, Chevron Techron, and Mechanic in a bottle. Make sure you have a good seal with the exhaust where it meets the head, can't believe air leaks downstream from that would be causing the popping or lean condition you describe. Idle runs on the pilot jet as you move up in the RPM range the needle & main jet come into play. Does it have a jet kit? if you're running an aftermarket header it would benefit from a jet kit, including a needle change. A jet kit will have grooves at the top of the needle, have you tried new clip positions? Raising the clip to a higher groove on the needle will lean the mixture and richen as you lower the clip.
Yeah, the carbs were pulled out and cleaned, and put back together. Used ultrasonic machine. It does have a jet kit. Spark plugs were replaced, new oil and filter, coolant drained and refilled, new air filter, new petcock, new fuel pump, one new hose on carb that looked rough. Also ran a little MMO in the first tank to help with any hoses that may have had any residue in them.


The exhaust has a leak at the header, seemed to get better when I loosened and wiggled it then tightened. IMG_4743.HEIC

Have to check for sound to see if it is still leaking there, but it is also leaking at the joints underneath where it splits. You can see here I can wiggle the pipes by hand IMG_5175.MOV
 

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Discussion Starter · #12 ·
You know the exhaust is leaking, and you know the exhaust is popping. Fix the leaks and see if that fixes the popping.
You could have a misfire but I wouldn't jump to that conclusion. Fuel additives are not a solution to this problem. They won't hurt it, but they won't fix exhaust leaks.
Definitely fixing those, just hoping that is the issue. But wondering what else could be done as well just in case.
 

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You're on the right path I believe. Don't forget to remove the old copper gasket in the head, they get stuck in there and you can easily put the new one on top of the old one causing another leak.
 

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Discussion Starter · #14 ·
You're on the right path I believe. Don't forget to remove the old copper gasket in the head, they get stuck in there and you can easily put the new one on top of the old one causing another leak.
The only issue I am concerned about is that rear pipe lol. Hear it is a pain to get to. I have a D&D exhaust I was thinking of replacing, not sure if they go bad and have no idea when it was added.
 

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Discussion Starter · #15 ·
To show how confusing this issue is. I just went out and fired it up, no issues. Started to ride and it popped a few times but then stopped.

Opened that thing up heavy back and forth up my block with no issues at all, I mean rode it harder than it has since the carb rebuild, and not an issue at all.

Checked for air leaks and can only feel one at the joints where it splits. Nothing at the top, nothing at exhaust can. Just the joints.

Question is, can it be something that happens as the bike warms up? But then the weird thing is I had it happen the first time when the bike was not warm.

So confusing.

Side note, since doing the carbs, the bike has not been ridden much at all and not even over 50. And I have not really opened the throttle much, smooth back roads riding.
 

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When the motor is cold it will generally be a bit lean which can causing popping. As the motor warms up it needs less fuel/more air, that is why you cut the choke off. Try ridding enough to go through a tank of gas. If it's running fine once warmed up ride it for a while and see what happens.
 

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Discussion Starter · #17 ·
When the motor is cold it will generally be a bit lean which can causing popping. As the motor warms up it needs less fuel/more air, that is why you cut the choke off. Try ridding enough to go through a tank of gas. If it's running fine once warmed up ride it for a while and see what happens.
Was thinking that today. Just keep riding and see if it goes away on its own. When it does do it I have to stop cause it’s bad. But gonna try going on a long ride and see what happens.
 

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Discussion Starter · #18 ·
So....

We took out the carbs and found a float bowl that was stuck. Fixed that. Bike ran great. Then started acting up again and on one cylinder.

I then thought about what happened the night before it all started. I had installed new led lights. The wires run right by the ignition coil. So that got me thinking maybe the connection is loose. Since this was so intermittent.

Played with them last night, and it was still running on one cylinder.

So then I just gave it some gas down my street. Had 2 big backfires and the other cylinder kicked in. Ran well all night after that.

I am thinking I had 2 issues. The float bowl was causing it to backfire so much with all that gas being dumped in.

Then, either I have a loose connection on the coil, or I had to clear something out of the lines.

We did rebuild the carbs and clean, new petcock and fuel pump, a few new hoses. But maybe there was still something in the other lines?

Will keep an eye on it and see if it happens again, may replace the coils if it does.
 

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Glad you are getting there. I cannot stress how important correct float heights are, non-sticking floats and non sticking, non-worn float needle valves are in Constant velocity carbs. Same goes for any leaks into the carbs from Air-box seals to carb and they also don't like exhaust leaks.

I've done a lot of work on CV carbs before on my old Hondas and these are some of my old pages. Different carbs but same principles,


BTW.

Once serviced correctly and running a shot of Sea foam/Redex or any fuel cleaner in every couple of three tanks I had one set of carbs on one of my Hondas that didn't need touching for over 10 years except a yearly or twice yearly balance check and reset :)

SV650 Carb Balance


.
 
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