How "lumpy" is "lumpy"?

Hello all,

Im a classic lurker, used the wealth of information on this forum for my own gain and Im going to keep on taking

So my question is, how lumpy is my sv650 99' ment to be?

At a constant speed between 3.5k to 5k Im getting small-meduim jerk once or twice a second and its driving me mad not know wheather this is normal.

Acceleration through this range is ok, as is everything above 5K. Idle is nice.

A bit of background information:
Been riding a FI YBR since Feb last year, took the step up a the SV in nov. . Had to take it back to the dealer a number of times due to running problems but its now running nicely apart from this.

Im on 33bhp (self made throttle movement limiting thing, not a washer) so wasnt able to test ride any other sv's and therefore no comparison.

This is my daily ride, 60mile commute, so I need solutions or my bike could have a short life!

Is this just the way things are or is this too lumpy?

Many many thanks sv riders!!!

Hiya

What is the service history on the bike? Does it do this in all gears?

Sounds like fuelling if anything at all.

As per my recent thread, mine does similar in 2nd occasionally, but FFS I forgot to check my choke earlier when I had the bike out.

Id describe my old symptoms similar to that, was a worn chain, would only be real noticeable when cruising slow ish at constant speeds. Carbs being balanced should help too if your chain is new, might as well clean and check choke too.

What is the easiest way to check for a worn chain, assuming one does not know how many miles it's done or previous care?

Is it as simple as "Still has adjustment left in it, + no tight spots" = OK or more to it?

[embee]

When everything is right the carby engines run nicely, no hiccups/lumps/coughs. However there are many things which can make them wrong, especially as they get on in years and maybe don't get the maintenance required.

Some of the things include -

sticking choke plungers - remove, clean, lube cables, replace any broken/rusted springs. Easiest to remove carbs to get them out.

Water in fuel - drain the carb bowls, check the fuel tank filler drain pipe for leaking into the tank (they can rust through and let water into the tank)

Carb balance - balance the vacuum on the 2 carbs using suitable gauges, get them as close as posible the same at closed throttle/idle.

Correct idle speed - should be around 1300rpm, you may prefer slightly higher.

Idle mixture - the nominal setting for adjustments is just that, nominal. You really need to adjust them while the engine is idling hot, but the screws are quite difficult to get at without an angled drive adjuster (specially made exactly for this job). If in doubt adjust them each exactly 1/4 turn richer from where they are (screw out/anticlockwise) and see what effect it has. You can put it back if it doesn't help.

Valve clearances - effects shouldn't be great but it does alter fuelling slightly atvery low load, can be enough to give odd misfires if other things add up.

HT leaks - as HT leads/plug caps and coils age they can get susceptible to arcing and misfires. First step is to spray with water dispersant like WD40 or ACF50. Might need replacements.

Spark plugs - small body plugs like in the SV are more susceptible to insulation breakdown than big 14mm jobbies. Fit a set of iridium plugs if it doesn't altready have them, they can slightly extend the tolerance to fuelling glitches common with carbs, something like £6 each from fleabay.

mine did that and it was water in the fuel.

Thanks for the replies so far people.

A little more history of the bike:
It covered around 3000miles from 1999 to 2003 since then it cover a grand total of 100miles odd.
One lady owner, always garaged, immaculate on the outside, but not so internally is seems.

(Ive put another 2000miles on it)

Rode it for about a month when I first got it, with no expirence of the bike I didnt know just how rough the thing was running, sent it back to the dealer when the idle jets clogged up.

He cleaned up the carbs discovering something green and "growing" in the rear float chamber. After this it ran quite a bit better but still not happy I eventually replaced the carbs.

Everything from the carbs up have been cleaned, checked and replaced as nessesary. Fuel tank was rusty inside, however I have thoroughly cleaned it and symtoms do not suggest this.

One thing causing concern, when I took the carbs off the was a lot of corrosion on oneof the rear inlet valves, probably due to the float "thing". The steam of the valve was ok, and the bike does not burn any oil.

Valve clearances on rear cylinder are ok, havn't checked front.
Have not done a compression test.
Have not been able to balance carbs yet.
Replaced both plugs just before I took it back to the dealer, since then the front is ok, but the rear is slightly fouled, carboned up and ever so slightly oiled. SLIGHTLY.
Replaced both HT and coils, symtoms unchanged.

I do not think its water in the fuel, I've ran it numbers of times after draining the tank etc.
I do not think its choke, replacing the carbs, symtoms unchanged.
Chain slightly on the loose side, but do not think its wear.

There is a slight "ffuuu ffuuu ffuu" sound comming out the exhuast, its very quiet so you can only hear it at idle, but its occurs in the same pattern as the "lumps" Im getting.

My main thought its a valve either sticking or the corrosion messing flow into the cylinder. Of cause its my last resort to take the head apart as this is a very major job.

Again symtoms.
Perfect idle
Perfect over 5K
Perfect meduim/high throttle
lumpy/ slight misfire / feels like your going over a small pot hole between 3k and 5k at a constant speed.
Happens in all gear but the faster you get the less noticeable, more momentum and all that.

As you say embee no lumps or hiccups should be felt. I think alot of people confuse lumpness with vibration, I understand there will be vibration with a v-twin but lumpyness is very differnet.

Originally Posted by hongman

What is the easiest way to check for a worn chain, assuming one does not know how many miles it's done or previous care?

Is it as simple as "Still has adjustment left in it, + no tight spots" = OK or more to it?

Tight spots and seeing if you can lift the chain off the rear sprocket.

[5hort5]

Well I'm not sure if it's any help but last time mine was running a bit lumpy it was that the airbox was exactly fitted correctly, worth a quick look if nothing else

[mikerj]

Originally Posted by Andy M.

There is a slight "ffuuu ffuuu ffuu" sound comming out the exhuast, its very quiet so you can only hear it at idle, but its occurs in the same pattern as the "lumps" Im getting.

My main thought its a valve either sticking or the corrosion messing flow into the cylinder. Of cause its my last resort to take the head apart as this is a very major job.

A leaking valve is certainly a possibility. Might be worth just checking the valve clearances; it won't show a burnt valve or seat, but excessively loose or no clearance would warrant further investigation.