Loss of power after doing -2/0 on sprocket change?

[luukasama]

Greetings all you awakening hibernators [myself included, ]!

I'm a bit of a late rider this season, due to still cool temps which makes me feel like it's winter (I get cold too easily). I've just recently done a small change/mod of my front (-2) and rear sprocket (0), as well as chain which looked rusted as all hell and didn't look like it was ever changed before. I can definitely feel the power change and am learning to control it so that I don't wheelie off the start. However, something seems off ever since I took all the fairings apart [thought I could have it repainted into a different color, but the paint shop tried to rip me off]. This is a two fold problem I think, so bare with the long post please.

As part of the fairing removal, I also emptied out the tank and removed the rubber seal and lock. When I put it back the first time, I ran into an issue of the bike suddenly losing all power on the highway. It started doing some bucking and then the engine just shut off. Restarting it took quite a few tries, as well as 45 degree tilting and shaking because it felt as if the engine wasn't receiving any gas and there was possibly some kind of a clog. This was during a 5hr weekend ride, where this happened 4 times consecutively on one stretch of highway. Managed to somehow make it back to town, dumped a whole bottle of seafoam into the tank and it seems like the problem disappeared, but I still feel as if something is wrong. Refitted the lock again, and retightened the screws to make sure it's not too tight and that it doesn't create a vacuum. Which brings me onto the second issue.

Possibly due to the above, since changing my front sprocket down 2 teeth (16 -> 14), I've gained more power, but it feels as if I lose some between 5 and 6 rpm. Maybe I'm being hyper sensitive, but it feels as if the power is there 1-5, nothing between 5-6, and onwards from there I feel power again. Has anyone ever had these problems? Could it be possibly due to me refitting the gas cap wrong again, and if so, what are the suggestions you guys would have to make sure I'm not starving the bike of air in the tank?

Thank you in advance

[Jim]

i would never go down 2 teeth in the front. a front sprocket that small is really going to be pulling the chain down.
you're better off doing -1/+2.

so answer your question, you'll probably gain more pickup in that RPM range, not lose it. you're only going to lose top speed and require to shift more frequently.

[TheIglu]

You probably have a sticking vent for the gas tank. That's your real issue.

Get rid of that -2 up front. It's junk and you'll get nothing performance wise out of it.

[luukasama]

A sticking vent? Do you mean that little cone that's attached to the underside of the gas cap? Noob here, so if you can please explain, I would appreciate it.

Also, is it really that bad to go down 2 teeth? The way I understood it, if you go down in teeth at the front, that's more power, and in the back, more top speed. I don't care about top speed, as I don't generally ride very fast unless on the highway, so I didn't bother changing the back sprocket tooth count, other than just replacing it because it came in a kit.

[Jim]

-1 tooth in the front = +2.5 teeth in the rear.

you're never gaining power from a sprocket change. the engine still pulls the same aount of hp. changing the gear ratio (sprockets) will just modify acceleration or top speed, depending how you gear your bike. FYI, your speedometer and odometer will now be inaccurate with your sprocket changes. the only way to correct it is to purchase a Speedohealer and dial in your % that you're off.

[Paul_E_D]

Really guys??? A 14 will be fine. Next set of chain/sprocket just go to a 15 and subtract a tooth out back. So -1/-1 from stock. It does make the bike feel snappier.

edited for innacuracy!

[Pigman]

EX500 -2 isn't that much......so thats not a real issue

[rolker]

FYI, your speedometer and odometer will now be inaccurate with your sprocket changes. the only way to correct it is to purchase a Speedohealer and dial in your % that you're off.

My EX250's speedo is connected to the front wheel, so assuming we're talking about an EX500 here and that it also has a front wheel driven speedo, a change in gearing will have no effect on it. On the other hand, a change in front wheel/tire size will affect the speedo.

[Jim]

crap, forgot about that. cool call roland

[TheIglu]

A sticking vent? Do you mean that little cone that's attached to the underside of the gas cap? Noob here, so if you can please explain, I would appreciate it.

Also, is it really that bad to go down 2 teeth? The way I understood it, if you go down in teeth at the front, that's more power, and in the back, more top speed. I don't care about top speed, as I don't generally ride very fast unless on the highway, so I didn't bother changing the back sprocket tooth count, other than just replacing it because it came in a kit.

Yup, the little flapper. As fuel exits the tank, if that little jobbie isn't doing it's job (or the holes behind it are clogged) then you form a vacuum in the tank. Once that vacuum is more powerful than the gravity pulling on the fuel down into the petcock, you have no more fuel getting to the carbs.

Also, check to make sure your carb vent hoses aren't kinked. Could be getting vapor lock when it gets hot.

If you didn't modify the engine in any way, you aren't getting any more power out of your sprocket change. You may accelerate faster, but you lose your top speed. Gearing isn't about power, it's about trade-offs. Making it geared lower means higher RPM's when cruising but more leverage for the engine to accelerate the bike faster. Higher gearing means less leverage for the engine but lower RPM's for the same given speed.

In all reality, with the EX500, you are just gaining more practice shifting by dropping the front 2 teeth. That engine doesn't really spool up fast at all, I'd almost say to go +1 up front if you want to get anything out of it. It's a high rotational mass engine.

[rolker]

crap, forgot about that. cool call roland

You're right about the first part, as Clayton reiterated.

[luukasama]

I meant to say acceleration, not power, sorry guys. Reason being is because my boyfriend has a Ducati Monster, 800cc, and I feel like a fricking chump that I can't keep up with him in acceleration. Now, before I get my ears scraped for trying to keep up with a more powerful bike, I don't quite need or want a bike as powerful as his. I just wanted to get a little more acceleration ability so that I can catch up to him when I fall behind. He told me that my DOHC engine should technically keep up or even overpower his SOHC bike, but I'm not quite that skilled enough to do so, so for the time being, I did the sprocket change.

As suggested, I will take a look at the carb hose and make sure that that's not kinking. About the sprocket. I noticed that there is a shaped rubber piece over by the front sprocket that's right below the chain. Now, is that so that the chain doesn't touch the metal? I was thinking about taking it off because I had a very curious thing happen to me. When I changed the chain, the rear wheel turned less freely than it did before, but I account that for the chain being new and not stretched yet. A few times I had an issue happen where once I shut the bike off, and walked it to a parking spot, it was VERY hard to move it or even turn the wheel once I got it on the stand. It required some force in order to turn the wheel. We chucked it up to the chain rubbing against that rubber piece we were just talking about, purporting to look at it later, and then went off on our way.

About half an hour later, we tested it again, and the wheel seemed to be easily turnable again. When we were realigning the back tire and tightening the chain, I made sure to triple and quadruple check the notches on both sides. Everything seemed to match up. Am I missing something here?

[Jim]

I noticed that there is a shaped rubber piece over by the front sprocket that's right below the chain. Now, is that so that the chain doesn't touch the metal? I was thinking about taking it off because I had a very curious thing happen to me. When I changed the chain, the rear wheel turned less freely than it did before, but I account that for the chain being new and not stretched yet. A few times I had an issue happen where once I shut the bike off, and walked it to a parking spot, it was VERY hard to move it or even turn the wheel once I got it on the stand. It required some force in order to turn the wheel. We chucked it up to the chain rubbing against that rubber piece we were just talking about, purporting to look at it later, and then went off on our way.

DO NOT remove the chain guide. it's there for a purpose. the reason you're experiencing friction is because your sprocket is so small, it's pulling the chain down & wearing the end of the chain guide. this is why it's been suggested to not go smaller than -1 on the front.

[rolker]

Reason being is because my boyfriend has a Ducati Monster, 800cc, and I feel like a fricking chump that I can't keep up with him in acceleration. Now, before I get my ears scraped for trying to keep up with a more powerful bike, I don't quite need or want a bike as powerful as his. I just wanted to get a little more acceleration ability so that I can catch up to him when I fall behind.

Don't worry about keeping up with him in a straight line. Catch up to him, pass him and leave him weeping in the turns! (Disclosure: I do have a small bike bias, in fact both my bikes combined have less displacement than yours)

As suggested, I will take a look at the carb hose and make sure that that's not kinking. About the sprocket. I noticed that there is a shaped rubber piece over by the front sprocket that's right below the chain. Now, is that so that the chain doesn't touch the metal? I was thinking about taking it off because I had a very curious thing happen to me. When I changed the chain, the rear wheel turned less freely than it did before, but I account that for the chain being new and not stretched yet. A few times I had an issue happen where once I shut the bike off, and walked it to a parking spot, it was VERY hard to move it or even turn the wheel once I got it on the stand. It required some force in order to turn the wheel. We chucked it up to the chain rubbing against that rubber piece we were just talking about, purporting to look at it later, and then went off on our way.

About half an hour later, we tested it again, and the wheel seemed to be easily turnable again. When we were realigning the back tire and tightening the chain, I made sure to triple and quadruple check the notches on both sides. Everything seemed to match up. Am I missing something here?

Do make sure you are not over tightening the chain. It needs enough slop to let the suspension (or in the case of an EX500, the frame?) work.

[OreoGaborio]

Do make sure you are not over tightening the chain. It needs enough slop to let the suspension (or in the case of an EX500, the frame?) work.

Ditto. Enough slack for at least an inch or so of vertical movement.

I cringe every time someone says "I tightened my chain"... I feel like for every chain I've seen that was too loose I've seen 1000 chains that were too tight.

[luukasama]

Will do, guys. I'll recheck the chain also. It seemed to me like it was fine, because we did do the loosening and checking the slack. I believe that there should be about an inch or so of movement. When I put in first gear on the stand, the chain swung a little up and down, so I would assume that that's enough of proof that it's fine. Anyway, couldn't hurt to triple check!

Another question for you guys: I want to repaint my bike into a different color. What would be better: bring it to a shop, or do it yourself? I do have a bit of a tight budget, and can't spend more than $200. I tried to take this into Maaco, but they upcharged me for something that would cost for a car, not a motorcycle and especially when I took the fairings off myself. Are there any shops that can do this at $200 or less around the Framingham, MA area that anyone can recommend?

[luukasama]

Hey, Iglu! You were right. I did a little research as well to cover all of my bases, but it was because the carb vent hose got kinked. I was halfway on my ride home with my boyfriend when I felt it bucking, loss of power between 5-6 RPM, and then it just became hard to move. Luckily we stopped by a park, so I was able to lead and walk it to the parking lot. Kiku wouldn't start at all. So my boyfriend went back home, got my saddle bags loaded with tools and came back. Took the tank off, then gently pulled on the carb hose and it wouldn't budge. So I was like, aaah! So it was the hose, because when we pulled it out, the bike started without issues and after revving it up some, didn't start dropping in the RPMs, and when idling, didn't shut off. Did a test by blocking the end with my thumb, and sure enough, we reproduced the choking right away. Didn't feel anything else bad, like bucking afterwards, or that lost off power. Still a little paranoid and will take the bike into work again tomorrow, but looks like your advice was right on the money. Thanks!

[Jim]

So does that mean you're ditching the -2 front sprocket?

[Degsy]

Wirelessly posted

Make sure that sprocket went on the right way around. You'd be surprised how many i see on backwards. That makes the chain track left and the rear wheel turns tighter.

[luukasama]

So does that mean you're ditching the -2 front sprocket?

Haha, not so sure I want to get rid of that, seeing as that's my second sprocket now, and I like my power. Got the first as part of a chain kit. It was bent, and kept rotating nilly willy, like a see saw. Got the second sprocket separately, but decided to go down 2 teeth because I wanted more acceleration. I wonder if it makes more sense to increase a tooth on the rear sprocket then? I've got a 41 tooth on right now, so I was thinking of the chain is the cause of the tire not turning as freely, then increasing the rear sprocket would help? In essence, -2/+1?

I've only now started to delve into gear ratios and what they mean. If people still suggest I go -1/-1 [from this point, it would be +1/-1], I'll do that on my next chain replacement. Of course, if I find that I'm still having trouble with the front sprocket, I will do the change a lot earlier. I want to see what it feels like now that I've resolved the choking problem

[luukasama]

Wirelessly posted

Make sure that sprocket went on the right way around. You'd be surprised how many i see on backwards. That makes the chain track left and the rear wheel turns tighter.

Yep, we've run into that problem also. The new front sprocket was flat on one side, and leveled in another. Like a dumb noob, I put the flat side against the bike and that made the tire near impossible to turn. Fixed that once we turned it around.

[TheIglu]

Hey, Iglu! You were right.

Of course I was. That's what I do. It's my thing.

Glad to help (you inflate my ego).

[DaveZX6r]

You are better off raising the tooth count in the rear than you are dropping the count in the front. When you decrease the front sprocket you are forcing the chain to turn a lot tighter and depending on the tooth count can cause chain noise, tightness rotating, or increased wear. As long as your slack is right the wear shouldn't be such an issue but you might find your bike is a little more picky about how much slack you run.
You did check your slack from the tightest point in the chsin right?
As said its all about gearing advantage. Less teeth in the front and or more teeth in the rear equals more leverage and quicker acceleration, but lower speed per rpm in a given gear. More teeth in the front and or less teeth in the rear equals less leverage and slower accelleration, with a higher speed for any given rpm in a particular gear.
Going minus one front and then minus one in the rear is counter productive. You are gaining leverage from dropping one in the front, then throwing some of it away by dropping one in the rear. You would be better off leaving the front alone and raising one or 2 in the rear for the same leverage.

Also you need to check your chain slack in neutral not in first. With the bike iether straight up and down or on a swingarm stand. Not the side stand. The side stand wont allow the suspension to compress naturally and may throw off your measurement.

[luukasama]

Hey guys, thanks for all the advice. Been really busy, so wasn't looking at the forums. Finally found the real issue as to why my bike decelerates like a mofo, and it was the stupid n00b mistake too. Egh, anyway.

When I was changing the chain/sprocket, I must've completely forgotten about putting the caliper frame back on the tab that is attached to the right swing arm. What basically happened is that the caliper kept sliding forward [rather than remaining stationary, like it should], and kept pinching the rear brake line. So everytime I had a sudden stop, or had a quick slowdown, neutral or not, I would have to completely stop and the caliper would shift back due to momentum, freeing up the line and letting the fluid free.

We found this out upon a much closer inspection. It wasn't evident from looking at it from up top because the swing arm hid the problem. Lucky for me, the caliper only pinched the protective rubber sleeve on the brakeline, not the pipe itself, so there was no damage besides the aforementioned one. Cannot believe I made such a dumb mistake putting the tire back on and not noticing how the caliper sat before. Since then, the problem has completely disappeared. Lesson learned, pay more attention next time.

[Pigman]

Yea....as a good measure i will give a good look over and sometimes Pics to help Fix it if there is a problem after or needing to revert back. And test it on the stand see if there is any issues or change that has occured after doing the work.. spin the wheel see if the break works, no wobble, binding or noises.

This also may save you a lot when you can catch an issue before you go flying down the street and no on the bike that is...

But you did catch it and fig it out and thats half the battle or Fun...