Chain tension effect in gear shifting

[Lukich]

Hello.

One thing that bothered me about my 2005 SV650 was that oftentimes, when I would switch gears, it would sound "crunchy", for the lack of a better word.It was not constant, but would happen on every ride. I spoke to a mechanic, who helped me adjust the clutch lever, but the problem still persisted, albeit to a smaller degree.

So, I spoke to another mechanic, who told me that my chain is very loose and that might cause the issue. It was indeed too loose, so I tightened it to spec and my shifting has gotten a lot better immediately. I feel a solid sound every time a gear is shifted and the crunchiness has gone away.

My question is - why? Am I just experiencing a placebo? I don't really understand how a loose chain would contribute to the way gears are shifted. I know that if it's too loose and you're starting up, a chain might move up and down and hit something, but when I'm changing gears, I have the clutch pulled in, so nothing should gets transferred to the drivetrain.

Thanks!
Luka

 

[stangmx13]

the clutch disengages the crankshaft from the gearbox. the gearbox is always engaged w/ the countershaft and therefore the rear wheel. the chain flaps around most when not under power, essentially when u are shifting. so i guess its possible that chain tension would affect shifting. but ive never felt it. i suspect this is at least partly placebo effect.

what might be of more help... the clutch lever does not need to be and probably shouldnt be pulled all the way in when shifting gears. the shifts will be more "positive" and feel better if u only disengage the clutch 1/2 to 3/4 of the way when shifting. its faster, smoother, and better this way. i move my clutch fingers ~3/4" when shifting. every bike is different, but u really want to be disengaging the minimum amount for a smooth shift.

 

[Schnellbandit]

Depending on miles on the bike, check the cush drive. Worn cush drive bushings can add slop into the driveline and also cause issues ( like contributing to faster chain wear).

They are usually inexpensive to replace if you do it yourself. If you are experiencing a lot of snatchiness check the cush drive.

 

[EEL]

How many miles on the bike?

Have you ever replaced the sprockets?

The cogs tend to warp (curl) in the direction of motion. When you shift, it intermittently unloads the chain. If the cogs are worn, the chain could slip a bit and then catch. Making a grinding noise.

Tightening it might seem like solving the problem but if the tension is beyond the spec for chain slack required by the manufacturer, you may have damaging effects on the transmission and output shaft seal.

 

[Lukich]

The bike has about 9000 miles on it. I looked on the sprocket teeth and they seem OK. I will post a picture later to get the hive mind opinion. The chain had slightly over 2 inches of slack when I got to it, I tightened it to about 1.75 inches on the centerstand. For some reason, shop manual only describes chain tension on the sidestand, but I got the 1.5-2 inches figure from youtube.

 

[KazMan]

I think the crunchy you may feel is that with a properly adjusted chain, after the gear shift, the drive to the rear tire is more closely timed with your input of acceleration with the throttle. However, when there is a lot of looseness, it takes some time for the chain to begin driving the wheel. Your timing of throttle and sensation of acceleration now have a pause in it. As the chain takes up the slack, the rpm's will be slightly higher when all slack is removed and the end result is a bit of a harsh engagement to go forward. This could be what you are interpreting as clunky.

Analogy would be a long train which takes off. The first car behind the engine takes off quite smoothly, but the 30th car in the sequence experiences a sudden jolt as it moves forward because of speed built up.

 

[stangmx13]

The bike has about 9000 miles on it. I looked on the sprocket teeth and they seem OK. I will post a picture later to get the hive mind opinion. The chain had slightly over 2 inches of slack when I got to it, I tightened it to about 1.75 inches on the centerstand. For some reason, shop manual only describes chain tension on the sidestand, but I got the 1.5-2 inches figure from youtube.

that might still be too much slack. quick searches show your manual says 20-30mm on the sidestand. just do the adjustment on the sidestand (or a rear stand) and put it at 30-35mm / 1.2-1.4"

 

[mototireguy]

that might still be too much slack. quick searches show your manual says 20-30mm on the sidestand. just do the adjustment on the sidestand (or a rear stand) and put it at 30-35mm / 1.2-1.4"

+1

A great final check it's best to check the chain slack with someone sitting on the bike. Chain slack tends to get tighter as the rear suspension compresses.

Some bikes with 1.5" of chain slack when unloaded will have near zero slack when someone sits on it.

 

[Lukich]

I think the crunchy you may feel is that with a properly adjusted chain, after the gear shift, the drive to the rear tire is more closely timed with your input of acceleration with the throttle. However, when there is a lot of looseness, it takes some time for the chain to begin driving the wheel. Your timing of throttle and sensation of acceleration now have a pause in it. As the chain takes up the slack, the rpm's will be slightly higher when all slack is removed and the end result is a bit of a harsh engagement to go forward. This could be what you are interpreting as clunky.

Analogy would be a long train which takes off. The first car behind the engine takes off quite smoothly, but the 30th car in the sequence experiences a sudden jolt as it moves forward because of speed built up.

I realized I probably didn't explain the situation correctly. The crunchy feel I get happened when I physically shift the gears by pushing the shifter, not when I let go of the clutch. I would think that it came from clutch plates not disengaging properly for some reason, but have no idea why tightening the chain made it better.

 

[KazMan]

interesting. Have you tried changing the oil or pulling side cover off to inspect basket fingers?

 

[Lukich]

interesting. Have you tried changing the oil or pulling side cover off to inspect basket fingers?

Not yet. My oil change is coming up in a couple of months, I'll take a look at it then. Might as well take a look at the basket and replace the plates, while I'm at it. Now that the chain tensioning magically fixed it, I'll probably wait until then.

 

[bunnygoat]

Chain tension effects shifting. You need proper tension to release and engage the gears smoothly. I noticed that especially going from a worn out chain to a new one.

 

[Busy Little Shop]

Too much chain slack negatively effects the smooth transition of power
because it upsets the suspension...

Too much throttle slop negatively effects the on off application of power...

Too much clutch drag negatively effects gear changes because your gears
can't shift smoothly if your clutch is part way engaged...

Here are the steps how to check your clutch for drag...
1 Place your bike on the center stand...

2 Start engine and establish a steady idle...

3 Squeeze in the clutch and hold... shift into first gear...

4 Now look at the rear wheel... if it's spinning step on the rear brake...
does this action drag down the engine rpms???

If you bike is equipped with an cable then adjust the clutch lever
knob clock wise (out) 1/4 turn and check again check for clutch
drag... if you bike is equipped with hydraulics bleed system and check
for bubbles...

Ultimately you want the rear wheel to stop spinning when the engine is
idling and first gear selected with the clutch lever is squeezed in...


You could also work on your technique...
Riders are after the same thing... smooth shift without upsetting
the suspension... the secret is to move the foot quicker than clutch or
throttle... go easy with the clutch and throttle but move your foot
quicker... but worry there is no such thing as too quick... its early
form of seem-less shifting...

 

[Schnellbandit]

Op, just thought of something else because I experienced it.

If you are heavy footed and not fast on the shifter lever you might get a crunch. I found this to happen more on the upshift on a smaller bike when I changed from riding shoes to full boots. The feel lost made me use more force and shift the lever slower.

Might help.

 

[Lukich]

Interesting, that might actually be it. I will try to compare slow shifting with faster one to see if it makes a difference.
Thanks!

 

[dravnx]

Try preloading the shifter. Hold your foot up on the shifter before you shift.

 

[afm199]

Sv is notorious for dragging clutch plates. They always make noise. The only time the clutch disengages completely is in the first 10k miles on new baskets and plates. After that they drag. Period.

 

[Lukich]

Thank you for your suggestions. It feels like Schnellbandit's suggestion was the main culprit. Preloading the shifter helps, too.