Re-Jetting SV650S

[catchsomesv650]

I've been lurking around in the forum for quite a bit. but despite my very limited knowledge of motorcycles, i've read several times about jetting the carbs once you get a full exhaust system.

i bought my 01 sv650s used and from what the mechanic says, the motorcycle has never been jetted.

so heres the thing. they say to re-jet the carbs, it'll be $200 labor and $100 parts. im a poor college student at san diego, so my question is

1. is it necessary?
2. what are the benefits?

edit: btw. i have a yoshi full exhaust

[petevtwin650]

I'll get my thoughts in before the people who actually know what they are talking about post. :p

I've been running my Sv with as full aftermarket system for 15,000miles+ with no APPARENT problems. No doubt the bike would benefit from a rejetting and dyno run but unless you really feel the bike is underperforming or the spark plugs are showing signs of a lean mixture then save your student dollars. :p

[catchsomesv650]

thanks for your advice petevtwin.

as long as it is not a ticking time bomb (ie. overheats the engine, increase engine wear, etc), then im okay not re-jetting. performance-wise, the bike is already fast enough for me :-)

[petevtwin650]

performance-wise, the bike is already fast enough for me :-)

That's because you already have the fastest Sv650s.





Blue and Curvy.:p:p:p

[tranx]

Not re-jetting wont harm the engine at all. All it will do is allow the engine to exploit the extra air flow made available by having an aftermarket exhaust, thus giving a touch more power/torque. Also if you don't re-jet when fitting an exhaust system it might actually damage the power output very slightly in the midrange. However its not the sort of thing you would notice without a dyno run.

[northwind]

I'd disagree, the difference in power when I fitted my race system was unmissable. I totally misinterpreted it, instead of feeling the loss of power in the midrange, I actually thought I'd gained power up top, making the midrange feel weak. Complete rubbish as it turns out, I was down on power everywhere and down about 6bhp at 5000rpm! But the brain reads contrasts not absolutes, so a gradual power curve usually feels weaker than a steep one, even when it's not.

Still, I have to ask, why would you fit an expensive race system and not rejet for it? A slipon would give you almost the same weight loss, be far cheaper, and wouldn't have any risk of sabotaging your power.

It's possible for a lean-running bike to suffer damage over time by the way... It'll also be running inefficiently, if it's lean enough, causing a loss of MPG.

The sensible thing to do with an SV is to leave it alone, frankly, a full system and rejet will net you, being optimistic, maybe 5-7bhp at best, depending on what filter you use, in return for several hundred pounds worth f parts and work. It doesn't make much sense. I did it myself with a £150 exhaust system, and a used BMC Race RS filter and DJ jet kit, total parts cost £220. Then I taught myself how to jet it, and did it, total cost 2 dyno runs, £30, to check my results, but a lot of my time. And even then it's hard to justify.

If you want a little more power, consider the cam swap instead, it's quicker, it's just as effective and it's much cheaper. If you want a LOT more power, either get a faster bike or start saving ;)

[ukhammy]

Your reply rings true with my thoughts too Northwind. Was thinking of a full system with induction kit for my K6. Then i took stock of the total cost, £600-£700 for a system, £80 for induction kit and probably another £200-£300 for dyno time/power commander. Very hard to justify, recent magazine article qouted extra 5hp at 6000rpm for a full race system. Remus Revolution slip-on on my shopping list now.

[Spanner Man]

Morning all.

In my 30+ years experience of playing with bikes one factor that stands head & shoulders above all others, is that the bikes that last the longest & have the fewest number of running problems are standard bikes with few modifications. An exception being an aftermarket Road legal exhaust, which is usually fitted for cost reasons rather than in an attempt to gain performance.

The long term effects of fitting say a race exhaust, are often not apparent until it's too late. Standard bikes usually maintain an adequate mixture under all riding conditions. Whereas a race exhaust on a bike with standard carburettors may appear to run ok, but may be running lean at a certain RPM & throttle opening, so if say your journey to work involves a reasonable distance on a dual carriageway or motorway at the lean point in the altered mixture, your engine will slowly eat it's valves! The cumulative effect of which may not be apparent for several thousand miles.

I agree with Northwind in that if you want to go faster buy a bigger bike.

Cheers.

[petevtwin650]

I agree with Northwind in that if you want to go faster buy a bigger bike.

Cheers.

But where's the fun in that? :p

[Zuki_soldier]

Just a quick question guys
Ive just fitted my new fuel slip on can with removable baffle

Is it a good idea to get the carbs set up if i intend to use the exhaust without the baffle quite a bit?
Cheers
Ian

[yorkie_chris]

Ive got the fuel one as well, theres a bit of a flatspot at 5krpm, and it hangs up on idle, so needs richening up slightly.

However its still rideable, and hasn't eaten any valves, yet.

However this might not apply to you, as I'm on 33bhp, which royally screws the carburetion over as it never really gets to the mains.

[toonyank]

Just a quick question guys
Ive just fitted my new fuel slip on can with removable baffle

Is it a good idea to get the carbs set up if i intend to use the exhaust without the baffle quite a bit?
Cheers
Ian

This would depend on the effects of the decreased back pressure (leaning it out). Contact fuel and see what they recommend.

What spanner man said still stands, the fewer the mods the longer the life expectency especially in 2 strokes, ouch I know the feeling.

Shouldn't be drastic with a can though.

[yorkie_chris]

The fuel like most slipons is supposed to run fine with no change to setup.
Dunno why mine is different as I've not heard any other problems with them

[Graveyard8516]

I have a blue flame exhaust and I get a flat spot around 5000rpm. What does this mean? What do I need to do to rectify this?


Sent from my iPhone using Tapatalk

[650]

I'd disagree, the difference in power when I fitted my race system was unmissable. I totally misinterpreted it, instead of feeling the loss of power in the midrange, I actually thought I'd gained power up top, making the midrange feel weak. Complete rubbish as it turns out, I was down on power everywhere and down about 6bhp at 5000rpm! But the brain reads contrasts not absolutes, so a gradual power curve usually feels weaker than a steep one, even when it's not.

Still, I have to ask, why would you fit an expensive race system and not rejet for it? A slipon would give you almost the same weight loss, be far cheaper, and wouldn't have any risk of sabotaging your power.

It's possible for a lean-running bike to suffer damage over time by the way... It'll also be running inefficiently, if it's lean enough, causing a loss of MPG.

The sensible thing to do with an SV is to leave it alone, frankly, a full system and rejet will net you, being optimistic, maybe 5-7bhp at best, depending on what filter you use, in return for several hundred pounds worth f parts and work. It doesn't make much sense. I did it myself with a £150 exhaust system, and a used BMC Race RS filter and DJ jet kit, total parts cost £220. Then I taught myself how to jet it, and did it, total cost 2 dyno runs, £30, to check my results, but a lot of my time. And even then it's hard to justify.

If you want a little more power, consider the cam swap instead, it's quicker, it's just as effective and it's much cheaper. If you want a LOT more power, either get a faster bike or start saving ;)

"don't waste your money for small gains"

"do a cam swap"

Make yer mind up, mate 😂