Reduced speed

[deano]

Hello,

I have owned my 2003 model GS500 from new.  However recently I feel that it may be lacking a bit of power in 5th & 6th gear.  I can get up to about 10,000 RPM in 4th but when I change to 5th & 6th it tends to go no further than approx 8,000 rpm.  Could this be due to wind resistance perhaps and the changing seasons here in OZ?  THe max speed I have ever managed out of my GS500 is 180 KMPH (according to the clock) but as an example today the max I could get was 150 KMPH on the freeway, on some roads it struggled to get to 140 KMPH.  Could this be to increased wind resistance, or an indication of something else?

I have done 16,000 KM on this bike and done all servicing except ever changing the air filter.  Also noticed a small amount of oil in the air box the other day! Is this to be expected?

[Roadstergal]

That doesn't sound right.  Mine accelerates decently in 5th and 6th, it'll hit 10K in 5th, and I only backed down from 110mph in 6th due to ticket fears.  I don't have oil on my filter element.

[werase643]

just for shits and giggles....
pull the filter and go for a ride.....
any better?
if yes...change the filter
if no put the filter back in

also ride at WFO for a few minutes...3rd--4th..5th....
pull over and pull a plug....what color is the tip?
white...light tan...black...dry...wet?

sounds like it is ...starving for air

[TR]

yeah, a plugged air filter may be the cause... even if it's not, since filter should be cleaned ever xxx miles/kilometers cleaning or replacing the filter won't harm and would let you find another reason confidently.

[deano]

I took the air filter out and went for a run.  The engine runs rough around 5000 6000 RPM without the airfilter.  Is this normal?  Think running it without the filter did not prove anything.  

As for plugs.  I took them out.  Both are tan, but not a light tan.

Thanks all for your responses.

just for shits and giggles....
pull the filter and go for a ride.....
any better?
if yes...change the filter
if no put the filter back in

also ride at WFO for a few minutes...3rd--4th..5th....
pull over and pull a plug....what color is the tip?
white...light tan...black...dry...wet?

sounds like it is ...starving for air

[Kerry]

I have done 16,000 KM on this bike and done all servicing except ever changing the air filter.

That's what - 10,000 miles?  According to my Haynes manual the filter is supposed to be cleaned every 2000 miles (3000 km) and replaced every 4,000 miles (6000 km).  Personally I think that's excessive, but it's the official spec.

Also noticed a small amount of oil in the air box the other day! Is this to be expected?

Actually - yes, it is.

I took the air filter out and went for a run. The engine runs rough around 5000 6000 RPM without the airfilter. Is this normal?

That's exactly how mine ran (and sounded) when I rode to work one day with no filter in it.  I was still noob-ish, and I really thought my dirty OEM filter would cause problems if I kept using it (or something like that), so I gave it a shot without.  It ran terrible (compared to with the filter in) and sounded very "throaty".  I decided that a dirty filter was far better than no filter and put it back in until about the 16,000 mile mark - when I briefly tried a (reusable) UNI and then settled on a (reusable) K&N.

Think running it without the filter did not prove anything.

It certainly proved that air filters are good things.    I think there is a reasonable chance that yours is a little too dirty.  Do you have access to compressed air?  To clean it: blow from the outside, through the mesh cage, toward the hollow center.  Alternately, Srinath says you can clean the OEM paper filter by soaking it in gasoline.  :dunno:

Is there any chance that you could borrow a new(er) air filter for testing?

[mp183]

According to Suzuki you should change the air filter every 7,500 miles that is for my 2002.  That can vary with your environment.  I would change it but don't faint whey you hear the price.

[Kerry]

According to Suzuki you should change the air filter every 7,500 miles[...]

Oops - I stand corrected.  That's what the Haynes manual says, too.  That'll teach me to spout things from memory!

So I guess I only used my OEM filter twice as long as I "should" have, rather than four times as long.  Whew!  

[deano]

Thanks for your response Kerry,

Yes I went out and purchased a new air filter (AUD$47.00).  Found a small amount of oil in the bottom of the air box, but this is normal according to other posts.  However I would have thought this would contribute to blocking the airfilter as I found light oil deposits on the intake side of the airfilter.

Went for a ride on the freeway.  Still find it hard to get the bike past 8,000 revs in 6th gear.  It will go to higher revs in 5th though.  I managed to get to 170KPH on some parts of the freeway but also noticed the speed drop back to 140 - 150 KPH in other parts when the wind resistsance was higher.  Am I expecting too much from my 2003 model GS? Or should I be able to get to 10,000 revs or even up to redline in 6th without too much effort?  I find if I am going up moderate hills I can slowly see the speed dropping away an have to eventually change down to 5th or 4th sometimes. Is this normal?

Checked plug colour and it is fine.

Any information please would be appreciated.

I have done 16,000 KM on this bike and done all servicing except ever changing the air filter.

That's what - 10,000 miles?  According to my Haynes manual the filter is supposed to be cleaned every 2000 miles (3000 km) and replaced every 4,000 miles (6000 km).  Personally I think that's excessive, but it's the official spec.

Also noticed a small amount of oil in the air box the other day! Is this to be expected?

Actually - yes, it is.

I took the air filter out and went for a run. The engine runs rough around 5000 6000 RPM without the airfilter. Is this normal?

That's exactly how mine ran (and sounded) when I rode to work one day with no filter in it.  I was still noob-ish, and I really thought my dirty OEM filter would cause problems if I kept using it (or something like that), so I gave it a shot without.  It ran terrible (compared to with the filter in) and sounded very "throaty".  I decided that a dirty filter was far better than no filter and put it back in until about the 16,000 mile mark - when I briefly tried a (reusable) UNI and then settled on a (reusable) K&N.

Think running it without the filter did not prove anything.

It certainly proved that air filters are good things.    I think there is a reasonable chance that yours is a little too dirty.  Do you have access to compressed air?  To clean it: blow from the outside, through the mesh cage, toward the hollow center.  Alternately, Srinath says you can clean the OEM paper filter by soaking it in gasoline.  :dunno:

Is there any chance that you could borrow a new(er) air filter for testing?

[Kerry]

Went for a ride on the freeway. Still find it hard to get the bike past 8,000 revs in 6th gear. It will go to higher revs in 5th though. I managed to get to 170KPH on some parts of the freeway but also noticed the speed drop back to 140 - 150 KPH in other parts when the wind resistsance was higher. Am I expecting too much from my 2003 model GS? Or should I be able to get to 10,000 revs or even up to redline in 6th without too much effort? I find if I am going up moderate hills I can slowly see the speed dropping away an have to eventually change down to 5th or 4th sometimes. Is this normal?

Everything you said describes my bike to a "T".  Redlining in 6th gear is almost unheard of.  170 KPH is about the limit, unless you're going downhill or have a tailwind.  (I've had mine up to 120 mph / 192 kph a couple of times, but at least one of the above applied in each case.)  Some folks find that they can reach a higher top speed in 5th gear because of the higher revs.

Does this mean that you'll be trading up soon?  

[deano]

Thanks Kerry,

I believe the change of airfilter has helped to a degree.  However I do find it frustrating that the bike speed can be so affected by changing wind resistance and moderate hills, even when at full throttle.   As an example on the freeway I may be in the process of overtaking at say 160KMPH but then struggle to execute the manouver due to above conditions and hence the speed may drop off to 140-150KMPH.  Amazing how much impact the wind can have!!!!

So you also find your speed dropping away?  Sometimes I have to change down to 4th on a hill.  

I don't have plans to trade up at the moment but it is clearance time here in OZ on new motorcycles so as an example a new Suzuki SV1000 can be bought drive away for approx AUD$12,000.00 or a Honda Hornet for AUD$12,000.00.  May trade up at the same time next year.  

Went for a ride on the freeway. Still find it hard to get the bike past 8,000 revs in 6th gear. It will go to higher revs in 5th though. I managed to get to 170KPH on some parts of the freeway but also noticed the speed drop back to 140 - 150 KPH in other parts when the wind resistsance was higher. Am I expecting too much from my 2003 model GS? Or should I be able to get to 10,000 revs or even up to redline in 6th without too much effort? I find if I am going up moderate hills I can slowly see the speed dropping away an have to eventually change down to 5th or 4th sometimes. Is this normal?

Everything you said describes my bike to a "T".  Redlining in 6th gear is almost unheard of.  170 KPH is about the limit, unless you're going downhill or have a tailwind.  (I've had mine up to 120 mph / 192 kph a couple of times, but at least one of the above applied in each case.)  Some folks find that they can reach a higher top speed in 5th gear because of the higher revs.

Does this mean that you'll be trading up soon?  

[RC]

However I do find it frustrating that the bike speed can be so affected by changing wind resistance ...

The force from the wind is proportional to the square of the wind velocity. One design equation is: F=(rho/2)*u^2*Cs*A, where rho is the mass density of air, Cs is the shape coefficient and A is the area of the object exposed to the wind.

Not sure about the wind force on rotating objects, like the wheels.

From what I've heard the Hayabusa shape is largely dictated by the wind.

In extremely strong head winds I have had to down shift to 5th to maintain or slowly accelerate.


R

[Kerry]

So you also find your speed dropping away? Sometimes I have to change down to 4th on a hill.

"YES" to the first sentence, "Hmmmm" to the second.

If you'll indulge me....

Back in 2002 my brother and I took a trip to British Columbia.  He was riding my 1996 GS500E with about 4,000 miles on it and I was riding my 1999 GS500E with about 15,000 miles on it.  When we came to a hill he would invariably be forced to shift down into 5th, and sometimes into 4th.  But I could take those same hills at one gear higher and even pass him!  :dunno:

Fast forward a couple years.  The 1996 -- now with ~10,000 miles -- had been sold to richard a few months earlier.  He started noticing reduced gas mileage, rotten performance on uphills, etc.  We checked his valve clearances (which I am ashamed to admit that I had never done before  ) and all four valves needed adjustment.  One of his exhaust valve shims was off by 4 sizes!

After the valves were taken care of, richard and I went for a test ride.  He felt like the bike performed OK, but he'd never been on most of those roads so he had no good reference point.

But the next time he commuted up the familiar I-15 route he came back with a big smile on his face.  He was able to take the hills in a higher gear, to maintain a higher average speed, etc.

So, if you have never done it (or had it done) consider checking your valves.  You might find some missing performance!

[deano]

Thanks for the advice Kerry.  I will check the valve clearances whn I get a moment.  However I do not have the shim removal tool (suzuki charge a lot for theirs!) so may try and lift camshafts if I need to change shims.

So you also find your speed dropping away? Sometimes I have to change down to 4th on a hill.

"YES" to the first sentence, "Hmmmm" to the second.

If you'll indulge me....

Back in 2002 my brother and I took a trip to British Columbia.  He was riding my 1996 GS500E with about 4,000 miles on it and I was riding my 1999 GS500E with about 15,000 miles on it.  When we came to a hill he would invariably be forced to shift down into 5th, and sometimes into 4th.  But I could take those same hills at one gear higher and even pass him!  :dunno:

Fast forward a couple years.  The 1996 -- now with ~10,000 miles -- had been sold to richard a few months earlier.  He started noticing reduced gas mileage, rotten performance on uphills, etc.  We checked his valve clearances (which I am ashamed to admit that I had never done before  ) and all four valves needed adjustment.  One of his exhaust valve shims was off by 4 sizes!

After the valves were taken care of, richard and I went for a test ride.  He felt like the bike performed OK, but he'd never been on most of those roads so he had no good reference point.

But the next time he commuted up the familiar I-15 route he came back with a big smile on his face.  He has able to take the hills in a higher gear, to maintain a higher average speed, etc.

So, if you have never done it (or had it done) consider checking your valves.  You might find some missing performance!

[glenn9171]

25 lbs. of torque will only push you so fast against a wind when you are doing nearly 100 MPH.  Especially when the combination of the bike and rider have worse aerodynamics than a truckload of cinder blocks.  

I found that dropping down to a 15 tooth front sprocket helped with more power at highway speeds.  Only about $15 US and 15 minutes to change with basic hand tools.  Well worth the small amount of work involved.  I experienced no appreciable loss of fuel economy with my 2001 model.

[Mk1inCali]

One thought, I recently installed Bob Broussard's ignition advancer, and that one change helped my otherwise stock bike so much it was almost disgusting on the freeway.  It runs along at 100-110 indicated like nobody's business and I can accelerate to 120 indicated easily.  I'm 6'5, 185-190 lbs, but I've got drag bars, so I'm tucked in pretty low.  After you check your valves, or before, either or....I'd recommend finding a Vance and Hines ignition advancer, or modding your plate.  I'm a believer!!!