Curvy sv650 down on power
 

Anybody got any suggestion what could be wrong with my sv650

It feels like it's down on power and really sluggish, someone said to me it's running rich but not particularly sure what he means by that.

I'll be great full for any advice. Thanks


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Re: Curvy sv650 down on power
 

I would suggest giving it a good service, eg re balancing carbs, run through some fuel system cleaner, check / replace air filter, new spark plugs etc

Running too rich means that your engine is consuming too much fuel for the amount for air that it is getting, so if that was the case I would suggest a new air filter, but also re balancing the carbs should help. Although if it was running rich I'm not sure if would be down on power but there are plenty of members who know a lot more than me on this subject.

How long since it was last serviced ?

Re: Curvy sv650 down on power
 

When was it last serviced or attended to in any way and what was done? Did the power loss happen suddenly, or was it gradual? Is it consistent or does the problem come and go? What was your typical fuel consumption and how does it differ - if it does of course - presently?
What prompted the running rich thinking? If true it points toward clogged air filter, punctured or sticking float, damaged or sticking float valve or possibly loose or unscrewed jet.

The more info you can provide the better the chance of a realistic diagnosis of the problem.

Re: Curvy sv650 down on power
 

Sorry for the vague info

The sv is a track bike and I was at cadwell today. The problem was on the straights it was struggling to get anything over 90mph. It was like it all day and this was the first time the bike had been used since back end of last year. Over the winter I changed the oil and oil filters but thats about it. The sparks plugs was done the begging of last year. I also noticed that the throttle response was particularly great either but wasnt sure weather to put both these symptoms together. The reason I said about running rich was purely because while i was waiting to go out for the first session one of the instructor said to me it smelt like it was burning rich. Now on the dinner break I went and spoke to the one of the guys who was doing suspensions setus etc, the first thing he asked was had I resprayed my petrol tank and is at happened id only had it done a month or so ago. So he thought its maybe dust from the respray that has got into the tank and clogged up the fuel filter.

Is this likely to be a cause ? and if so how hard a job is it to replace the fuel filter.

Thanks

Re: Curvy sv650 down on power
 

Did you pull the spark plugs out and look at them? What did they look like?

Re: Curvy sv650 down on power
 

Not yet, didn't get back till late so lost the will. I managed to get the tank propped up at the track to make a quick check i hadn't kinked any pipes when replacing the tank. Ill check the spark plugs when I strip it down.

Curvy sv650 down on power
 

I think it would be best to start at the obvious, check the plugs, filters and the fuel flow. The two diagnoses you have had are quite exclusive; rich from one, obstructed fuel flow from the other. Now that we know it struggles at high speed I would tend to favour the second - insufficient fuel flow. Not necessarily for the reason given of course, but it's clearly worth checking. As you say it's been sitting unused for a few months then clogged up anything and everything in the carbs and fuel system is what I suspect is causing the problem.

Re: Curvy sv650 down on power
 

Check the pad under the tank has not fallen across the entrance to the airbox, this would strangle the engine big time.

Re: Curvy sv650 down on power
 

Dead easy, turn tank on it's side, take the vacuum tap out and blow any crap off.

Re: Curvy sv650 down on power
 

Did you use the choke lever?
If so, did the choke fully close when you returned it?
You DID return it, didn't you?

Re: Curvy sv650 down on power
 

I used it first thing in the morning when the bike was cold. Yea it was returned but somebody at work mentioned that it may be worth investigating that its functioning properly. Gonna get the tank up tomorrow and start by having a clean of the filter and go through from there. Hope its nothing to serious.

Re: Curvy sv650 down on power
 

So tonight we had a good look around the accessible areas:
1) Spark plugs - Front was finger loose when taking it out, sooty looking too on the spark end. We swapped it for a spare and got it tightened up, no cross threading either.
Rear seemed fine and was tight.
2) Air box, again no restrictions obvious, filter looks good, the box itself has a little oil in it.

http://i16.photobucket.com/albums/b1...psf636b0c2.jpg

3) The fuel filter was clean, we tested the petcock off the bike using a syringe to open the vacuum valve and fuel flowed freely out of the tank.

http://i16.photobucket.com/albums/b1...ps8bda2582.jpg

4) All vacuum pipes and fuel lines are in good condition and the bike was tested with the tank raised to make sure nothing was kinked with it down.
5) The battery terminals were cleaned as they looked a little crusty.
6) The choke was fully pushed back but we didn't look into the carbs themselves to see what the choke was doing at the end of the cables.

After which the engine was sounding like this, question to you guys is, does it seem right or do we still have a lot of hesitation, we seem to think it may have improved but we're not sure if we are imagining things!!

Thanks for the input so far, all help gratefully received.

Curvy sv650 down on power
 

A loose plug won't fire correctly, carbon builds up on the gasket face and stops it connecting to the engine case completely.

Re: Curvy sv650 down on power
 

do we need to go back and remove the carbon build up somehow?

Re: Curvy sv650 down on power
 

When you started it, was there a strong smell of petrol and black smoke.
Recheck stage 6 & make sure the choke plungers return fully when the choke is closed.

Re: Curvy sv650 down on power
 

Should have shown this too, its the front spark hole:

http://i16.photobucket.com/albums/b1...ps3369abdc.jpg

Re: Curvy sv650 down on power
 

No black smoke, some funny smells but not like petrol.
Are the choke plungers easy to see properly?

Curvy sv650 down on power
 

Unlikely, unless it's been doing it for a very long time, the action of screwing the plug in will have wiped it away and now there will be metal to metal contact. Won't hurt to pull the plugs and clean them anyway, the plug condition might provide some info too.

Re: Curvy sv650 down on power
 

The front spark plug came out dry but sooty, has been replaced by a good looking spare.

This will be the choke plunger then and we should be able to get those out and take a look: (Image from another thread)

http://www.sv650.org/derestriction/d...50K2_step6.jpg

Re: Curvy sv650 down on power
 

Look at it on a parts list - Robinson have one to look at / download.
You'll see it has a splitter just inside the left hand top frame rail. It's notorious for sticking.
Best way to check is probably by 'feel' - when you close the choke lever you SHOULD be able to feel the cable is a fraction slack at each carb, just like the clutch cable should.

Re: Curvy sv650 down on power
 

If the bike has been standing for a long while, it's probably worth stripping and cleaning the carbs. My dads curvy often runs like a dog when started after standing unused for a few months, and it's always been carb related.

Curvy sv650 down on power
 

Thanks, the plan is to start stripping the carbs to clean over the weekend. Hopefully as you say that will sort things out.



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Re: Curvy sv650 down on power
 

We got the carbs out, initial inspection doesn't show much wrong inside them, jets coming out tomorrow for further inspection. Fingers crossed it'll be purring again shortly.

http://i16.photobucket.com/albums/b1...ps026a40c8.jpg

Re: Curvy sv650 down on power
 

Hi All, so when looking at the jets and float bowls there was nothing really dramatic to report but we gave them a good clean and blow out with carb cleaner etc.

On testing the Throttle Position Sensor however, following the service manual we should have a range of 3.5k - 6.5k ohms on reading 1.
We ALWAYS have 5.25k ohms no matter where the throttle is.
(Tested with the sensor mounted and removed from the carb)

The second reading as seen in the manual does appear to be ok, it ranges from 0.5k - 5k ohms.

Could this cause our loss of power and hesitation issues? I'd like to think it would! Am I right in thinking this would affect ignition timing?

Re: Curvy sv650 down on power
 

Having read the manual a few times, I may have misunderstood, maybe the first measurement is always constant, and its the relationship of the second reading at WOT which is important.

Any thoughts:

http://i16.photobucket.com/albums/b1...pscf34aa91.png

Re: Curvy sv650 down on power
 

The sensor is a potentiometer with a resistive track between 2 pins (Ohms1), and a wiper contact which slides over the track and thus gives a varying resistance between the wiper pin and the end of the track (Ohms2).

Ohms1 will be a fixed value, somewhere between 3.5k and 6.5k Ohms. The actual value depends on the manufacturing. In your case the track resistance is 5.25k Ohms, that's fine.

At full throttle your Ohms2 reading should be adjusted to give 78% of 5.25k by slackening the fixings and turning the whole pot. IIRC there is actually very little adjustment available in the slots but it should get within range.

Re: Curvy sv650 down on power
 

Great answer, thanks a lot.

OK then back to head scratching.

Re: Curvy sv650 down on power
 

Also, the TPS makes an incredibly tiny difference