[Usagi on the Moon]

I've made a reddit thread about this before before coming here but essentially it seems like my SV650s has an issue with going to higher speeds. I've answered various questions/troubleshooted things over there so I'll post the link to the thread and shorthand some of the general info.
https://www.reddit.com/r/SVRiders/comments/y3vmu2 I’ve noticed when I take the freeway that whether in 5th or 6th gear, I can’t get rpms to exceed 6k and I can’t get the bike to go faster than 65. It feels like the top end of my bike is completely missing, I know this model is capable of more, the clutch and throttle free-play seem fine, the drain holes aren’t clogged and my spark plugs are good.
In addition I've just cleaned both the Petcock and Fuel Filter, the slides on the carbs seem to be functioning and while I haven't used any tools to check I don't believe there to be a vacuum leak. The carbs jets were ultrasonic cleaned only a few months ago, both cylinders seem to fire and get warm and spark plugs are very new.
Thanks in advance!

 

[Geo Smith]

In gears 1-4 can you rev past 6,000 RPMs?

 

[Usagi on the Moon]

In gears 1-4 can you rev past 6,000 RPMs?

Yeah I am able to do so up until about 5th and 6th.

 

[golden chicken]

Yeah I am able to do so up until about 5th and 6th.

Can you go over 65 in 4th?

 

[Usagi on the Moon]

Can you go over 65 in 4th?

Unfortunately I cannot. Once it hits 60-65 it feels like I hit a wall of sorts.

 

[golden chicken]

Unfortunately I cannot. Once it hits 60-65 it feels like I hit a wall of sorts.

For you to not have the power to go faster than that in basically any gear I'd be looking at fuel supply, carbs, etc. Do you have any history of the bike before you began the rebuild?

 

[Usagi on the Moon]

I got the bike secondhand, seller was shady and it’s been an uphill battle. So, no history other than it ran really really rough, especially at idle.

 

[golden chicken]

Sounds like a thorough carb cleaning, rebuilding, and balancing is in order.

 

[Usagi on the Moon]

Carbs were cleaned and rebuilt twice, once by me a novice mechanic with aftermarket jets, a second time by a local shop that cleaned the original jets and put them back in.

 

[golden chicken]

Barring a major mechanical issue it almost has to be fuel related on a first generation SV. have you checked the strainer on the petcock, the petcock diaphragm, and the fuel pump?

 

[Geo Smith]

Sounds like a lot weirder (IDK if that's a word) issue than carbs. Usagi can rev past 6,000 RPMs in gears 1-4, but in taller gears he cannot rev passed 6k. That's odd indeed.

 

[golden chicken]

Sounds like a lot weirder (IDK if that's a word) issue than carbs. Usagi can rev past 6,000 RPMs in gears 1-4, but in taller gears he cannot rev passed 6k. That's odd indeed.

I agree it's a strange symptom.

On my 2gen SV, 65 mph was around 6500 rpm in 4th, if I remember correctly, so if the bike doesn't have the power to go 65 it isn't going to rev over that in any higher gear.

I'm starting to wonder if the fuel flow is restricted and the bowls are running out at high demand, which is why I asked about the strainer, petcock, and pump.

The other thing I'm unfamiliar with is that I know Japanese motorcycle licenses are tiered, but I'm not sure if there were various versions of restricted SV650 available there. I did find old post from other British owners who said they can still go over 100mph indicated on their restricted SVs.

 

[VFR4Lee]

It's not a bad throttle by wire control unit like my last bike.

 

[Geo Smith]

But if you can rev 10000 in 2nd, but only 6000 on 5th, strange stuff going on.

 

[Usagi on the Moon]

I was even able to redline in first but only up to 11,000, I don’t know if I’m supposed to be able to go higher than 11k but I did try. (Don’t worry, I didn’t do it unreasonably)

 

[Usagi on the Moon]

Addendum, yes the filter and petcock were dirty, some debris and yes after cleaning them the bike ran better but unfortunately it didn’t fix the issue.

 

[Usagi on the Moon]

One thing I’m confused about, I’ve taken apart the fuel petcock and fuel pump, but I keep seeing people mention a strainer and I don’t see one on my bike or anywhere in the manual so I’m confused by “mesh” filter or “strainer”.

 

[GeorgeRYoung]

Are the slides free to rise and fall?

 

[Usagi on the Moon]

In my personal tests both with my fingers and the throttle opened the slides and they closed just fine, people on Reddit said if they didn’t make a “thud” sound then there’s likely not a vaccum leak as well.

 

[Troy Jollimore]

How’s the seal on your airbox, or is there any mods done to it? Since you can rev high at all, the ignition or electronics aren’t at fault, unless it’s some weird speed limiter. Which is unlikely. It sounds like giving your entire fuel system a good once-over is in order, but if airflow is messed up at that particular speed, that’ll kill engine power as well.