Yamaha Starbike Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
67 Posts
Discussion Starter #1
I want to understand deccel popping better.
I'll give you an example: Last week it was around 110 degrees here in OKC and then on the weekend the temperature went down to about 85 degrees. I've been using 91 octane gas, you know to keep the bike running cooler. Well, when I got out that morning to go for a little ride the bike was popping like a pack of dogs. About two miles down the road, getting ready to enter the freeway I was down shifting into 2nd and commented in a turn when the engine popped back with enough force to kill the engine. The back tire stop turnning and I thought I was going down, but pulled in the clutch and regained momentum. Anyway, I went for about a 50 mile ride and when I got back everything was good. I topped off with some 87 octane gas.
Here's my question. I've read a few threads where people claim that certian types of exhaust can stop deccel popping. Is that posible? Isn't the EXUP valve suppose to do that? You know restrict the exhaust more. What are the smarter ways of controlling deccel popping?
 

·
Registered
Joined
·
422 Posts
Decel popping is all in the tuning. Even a stock bike pops but it is so muffled its not loud enough to stand out. when its hot the air is less dense which in turn richens up the fuel air mix, and cold air is more dense so you get a leaner mix, it can also be related to a leaky exhaust gasket. if air gets into the exhaust the oxygen will cause the raw fuel in the exhaust to ignite. The stalling is a completely different problem with the liners unrelated to the decal popping. the only fix for the stalling is installing a power commander and adjusting the the idle screw. i will find the site with the fix and post it.
 

·
Registered
Joined
·
67 Posts
Discussion Starter #3
HTML:
 it can also be related to a leaky exhaust gasket
Whats your perfered method to check for an exhaust leak?
 

·
Banned
Joined
·
4,088 Posts
HTML:
 it can also be related to a leaky exhaust gasket
Whats your perfered method to check for an exhaust leak?
do a real good cleaning around the exhaust flanges and ride it normally for a few nice weather days. Then look around the exhaust flanges for soot.

+1 on the engine doing a flat line entering or in a corner. I had it happen only once, I can't remember the air temperature but it was not hot outside, I'd have to say low 80's if there was a gun to my head. But it happend during a rapid decel entering a 90 degree turn into a side road. My clutch was getting pulled in at the very same time so I just jabbed the start button and was back in business before I came out of the turn. Even trying to duplicate the event many times after that same day, I was never able to make it happen again. Nor has it happened since. I've been told it's a microsecond pause in the ECU's ability to revive the engine into it's minimum idle RPM range and keep it alive. Not an actual scientific number but for coffee table talk it won't happen 99.999% of the time.
 

·
Registered
Joined
·
422 Posts
do a real good cleaning around the exhaust flanges and ride it normally for a few nice weather days. Then look around the exhaust flanges for soot.

+1 on the engine doing a flat line entering or in a corner. I had it happen only once, I can't remember the air temperature but it was not hot outside, I'd have to say low 80's if there was a gun to my head. But it happend during a rapid decel entering a 90 degree turn into a side road. My clutch was getting pulled in at the very same time so I just jabbed the start button and was back in business before I came out of the turn. Even trying to duplicate the event many times after that same day, I was never able to make it happen again. Nor has it happened since. I've been told it's a microsecond pause in the ECU's ability to revive the engine into it's minimum idle RPM range and keep it alive. Not an actual scientific number but for coffee table talk it won't happen 99.999% of the time.

Mine will generally flatline when i flick the throttle while downshifting. Doesn't happen all the time , but I can duplicate it. I just got to know my bike and ride accordingly. DO NOT try and pop start it by dumping the clutch, you WILL be sorry. It will lock the back tire right up.
 

·
Registered
Joined
·
1,452 Posts

·
Registered
Joined
·
672 Posts
Do tell us more on why and tell why to use higher octane fuel.
To decrease the chances of detonation due to high compression ratios. Sure, heat adds to the possibility of detonation but, a higher octanes properties do not fight that by way of being a coolant. It does so by being chemically more difficult to detonate under compression.
 

·
Registered
Joined
·
396 Posts
Higher octane does not equal cooler running

Higher octane does not equal cooler running. :)
you are correct. octane does not make your bike run cooler. it prevents detonation which can cause engine damage. it also doesn't make more power than regular gas. the only reason you would feel it makes more power is that the motor is running properly because of the controlled combustion. you lose power when the engine "detonates" because the detonation typically happens before the spark plug actually fire's the air/fuel mixture, pressure in the cylinder is so high before it reaches top dead center that the motor has to fight against this and you lose power. this is an uncontrolled combustion due to low octane. firing much like a diesel engine from hot cylinder air. this is why you don't see 12:1 compression motors on the road and why most motors don't come over 9.5:1 compression. you would need higher octane fuel standard at the pump. this is why you should never run 87 octane fuel in your bike. detonation is like smacking the top of the piston with a hammer. it can cause piston damage and can also flatten the bearings which can cause you to throw a rod. not good. for the extra few cents it costs why take the chance. if premium is .35 cents more than regular that's a $1.57 more IF YOUR TANK WAS BONE DRY. i usually fill when the light comes on and thats 3.75 gal x .35 = 1.31, i don't think that's going to break anyone's bank.
 

·
Registered
Joined
·
396 Posts
Twitching the throttle

Mine will generally flatline when i flick the throttle while downshifting. Doesn't happen all the time , but I can duplicate it. I just got to know my bike and ride accordingly. DO NOT try and pop start it by dumping the clutch, you WILL be sorry. It will lock the back tire right up.
mine has died suddenly a couple times from the same deal as you stated. when giving the motor a quick snap of the throttle it will sometimes backfire or miss. the other day it happened and locked the back tire up solid. it took a bit to get it started, i would assume the air box was filled with dead combusted air and i had to crank this out so oxygen could get back in to re-fire.
 
1 - 10 of 10 Posts
Top