Coughing/Sputtering

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Mike W

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I picked up a stock 94' Vmax this summer. Nice bike. It has 21K on the odometer. It runs great except for two minor annoyances. (1) It occassionaly coughs a bit at low rpms when I take off from a stop. (2) Right around 70 mph there is a bit of a jumpy spot in the power band where the bike feels a slight bit surgey.

I just got a synchronizer and hoped that synchronizing would take care of both issues, but it didn't.

What is the likely problem/solution? Oh, I have a K&N air filter in. Will adjusting the valves solve my problem?
 
Mike W said:
I picked up a stock 94' Vmax this summer. Nice bike. It has 21K on the odometer. It runs great except for two minor annoyances. (1) It occassionaly coughs a bit at low rpms when I take off from a stop. (2) Right around 70 mph there is a bit of a jumpy spot in the power band where the bike feels a slight bit surgey.

I just got a synchronizer and hoped that synchronizing would take care of both issues, but it didn't.

What is the likely problem/solution? Oh, I have a K&N air filter in. Will adjusting the valves solve my problem?

I am no expert but adjusting the air/fuel mixture might help, it might be too lean, try turning each screw slowly 1/8 of a turn counter clock wise to make it richer and ride the bike to see the difference.
Note: the bike will not run smooth until it is fully warmed up so don't forget that.
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iolite review
 
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Check your airbox,carb and vboost boots for cracks or leaks.Did you look at your diaphrams for rips or tears?Hold them up to a light and see if any comes through.
 
the surging could be the v boost kicking in, at what RPM do you notice this surge?

And you could also check the carbs. That is relatively low amount of miles for a 94. If it sat for a while the carbs could use a cleaning, or maybe even the fuel filter
 
I don't know a lot about the history of the bike, but it seems to have been well maintianed. It is very clean, and the rubber rings around the carbs show no signs of cracking.

The freeway surging is just over 4000 rpms, so it is not the Vboost.

When I synched the carbs with the Carbtune 2 (very nice tool!), I set them all around 22. I notice the Vmax manual says that I should set them around 26. Maybe that is the problem. I will try that adjustment.
 
I wouldn't pay that much attention to the sync readings. I just make sure all four are the same. Your reading sounds fine, mine is about 22 as well. It would go up or down depending on valve adjustment.

4000 rpm is low end carb circuits and just starting to transition into the needle. I would check your float level and clean the idle circuits. Check your coasting enrichers too.
 
Ok, I just synched the carbs again, and I now see that it is not possible to get away from 22 as my balance point since the #2 carb does not have an adjusting screw.

I put in a new fuel filter last week. The previous owner said he had the carbs cleaned 2 years ago.

Would you recommend Seafoam or some other fuel additive before pulling the carbs?
 
Seafoam is what I use, good results with it.

Buy some straws and an eye dropper. Warm the bike up. Take the top of the airbox off and stick the straw in pilot air jet #1. It's the jet at 1:00 when facing the bike. Take eye dropper and draw up several drops of seafoam. Put the Seafoam into the straw and then rev the bike. This method works better than the shotgun IMHO. This "peashooter" method cleans both pilot air jets, the pilot fuel jet and the main idle passage where the bypass holes and mixture screw exit from. The bike will pop a bit and will smoke for a few seconds. You can drop a few drops of seafoam in the choke plunger vent too just to be sure.

Use the shotgun if that doesn't work. If doing the shotgun, pay attention to the purge jets. These holes are very small, easy for dirt to get caught up in them.
 
firefly said:
I am no expert but adjusting the air/fuel mixture might help, it might be too lean, try turning each screw slowly 1/8 of a turn counter clock wise to make it richer and ride the bike to see the difference.
Note: the bike will not run smooth until it is fully warmed up so don't forget that.

I turned the air/fuel mixture screw a quarter turn counter-clockwise, and it seems to have taken care of the problem. Unfortunately, I got a speeding ticket last night when I was testing it out. :damn angry:
 
Mike W said:
I turned the air/fuel mixture screw a quarter turn counter-clockwise, and it seems to have taken care of the problem. Unfortunately, I got a speeding ticket last night when I was testing it out. :damn angry:

sorry bro, I just had one too and took an on line traffic school thing, it was $220 for that one.
but that means your max is alive:rocket bike:
________
Dallara SP1
 
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maleko89 said:
Seafoam is what I use, good results with it.

Buy some straws and an eye dropper. Warm the bike up. Take the top of the airbox off and stick the straw in pilot air jet #1. It's the jet at 1:00 when facing the bike. Take eye dropper and draw up several drops of seafoam. Put the Seafoam into the straw and then rev the bike. This method works better than the shotgun IMHO. This "peashooter" method cleans both pilot air jets, the pilot fuel jet and the main idle passage where the bypass holes and mixture screw exit from. The bike will pop a bit and will smoke for a few seconds. You can drop a few drops of seafoam in the choke plunger vent too just to be sure.

Use the shotgun if that doesn't work. If doing the shotgun, pay attention to the purge jets. These holes are very small, easy for dirt to get caught up in them.


That "peashooter" method sounds interesting we will call it Mark's peashooter, seriously can you provide some photos of it, simple and less invasive, I like that:clapping:
I am now a regular seafoam user thanks to you, it works well and keeps things clean! thanks Mark.
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herbalaire vaporizer
 
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Nah, not my idea. Paul Czernics told me about it. I'll get some pictures....ane we'll see if I can post 'em here.
 
maleko89 said:
Nah, not my idea. Paul Czernics told me about it. I'll get some pictures....ane we'll see if I can post 'em here.
I've been having the same problem.... my air / fuel screws are out 3 full turns now.
It isn't as bad as when they were 2-1/2 turns.
Should I go another 1/8 turn each?
I have the colortune but I can't for the life of me see the "difference" in the color of the spark.
BTW....Yes, I sync'ed the carbs and did the shotgun...all 4 diaphrams are new.....I also own a carbtune II ....AWESOME tool (considering in MHO the colortune sucks....anyone wanna buy it?)
I think from now on I'll do the eye dropper method instead of the shotgun....the shotgun takes too long.
 
Dreamster66 said:
I've been having the same problem.... my air / fuel screws are out 3 full turns now.
It isn't as bad as when they were 2-1/2 turns.
Should I go another 1/8 turn each?
I have the colortune but I can't for the life of me see the "difference" in the color of the spark.
BTW....Yes, I sync'ed the carbs and did the shotgun...all 4 diaphrams are new.....I also own a carbtune II ....AWESOME tool (considering in MHO the colortune sucks....anyone wanna buy it?)
I think from now on I'll do the eye dropper method instead of the shotgun....the shotgun takes too long.

Man I fiddled with that colortune thing and modified it to finally work, here is what it shows blue flame from 1/4th turn all the way to 4.5 turns then flame becomes yellow, so I set it at 4 turns, after a week the 4 plugs were fouled up so I gave it to Mark after I broke his and I am very happy since then, I sleep better and even lost a some weight:))))
________
City Turbo
 
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so I take it the colortune isn't popular with you neither?
I felt the same thing..... I was under the impression that it was "more advanced" like the carbtune II.
So, what did you finally put your screws at?
Do you think I should turn mine out another 1/8 turn or just go to my local yamaha dealer and have them use a sniffer?
AND.... whats the chance that all 4 DO NOT need to be set all the same turns?
BTW... my local dealer is good AND friendly... no horror stories here.
Good friends with the owner (family run dealer)
Randy
 
Dreamster66 said:
so I take it the colortune isn't popular with you neither?
I felt the same thing..... I was under the impression that it was "more advanced" like the carbtune II.
So, what did you finally put your screws at?
Do you think I should turn mine out another 1/8 turn or just go to my local yamaha dealer and have them use a sniffer?
AND.... whats the chance that all 4 DO NOT need to be set all the same turns?
BTW... my local dealer is good AND friendly... no horror stories here.
Good friends with the owner (family run dealer)
Randy

I took it to the dealer and the best adjustment was made by ear!
I once took it to another dealer to be tuned by a sniffer, the bike did hesitate at small throttle opening and I did not like it so went back to my regular dealer and let him adjust it again by ear and got him a nice gift,

The sniffer tuning is basically set on the leanest possible which is not necessarily good.
Let the dealer do the A/F mixture setting and a carb sync, then after that do your syncing with carbtune and FOLLOW the manual.
Note: the A/F mixture adjustment will remain good as long as you don't change anything else like a stage 7 or exhaust systems.
________
Ford Explorer history
 
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firefly said:
I took it to the dealer and the best adjustment was made by ear!
I once took it to another dealer to be tuned by a sniffer, the bike did hesitate at small throttle opening and I did not like it so went back to my regular dealer and let him adjust it again by ear and got him a nice gift,

The sniffer tuning is basically set on the leanest possible which is not necessarily good.
Let the dealer do the A/F mixture setting and a carb sync, then after that do your syncing with carbtune and FOLLOW the manual.
Note: the A/F mixture adjustment will remain good as long as you don't change anything else like a stage 7 or exhaust systems.
Just got back from "testing" my bike out....the coughing up thru the carbs is gone but when I run or rev high rpm's....say around 6 grand in 1st and the back off to idle it pops from the exhausts..... with flames!
My screws are set at 2 full turn out again....tried 2-1/2, 1 and also 1 1/2 out.....possible the timing is off?
 

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