Hi all, been working on a VMax 500 DLX that I bought used a couple of years back. The sled has 4000 mi but has never run right in the 5 years I've owned it.
Sled idles fine and runs ok at WOT but has extremely poor mid-range (3/4 throttle to run 30 mph). Gas mileage is poor at 6+ mpg and oil usage is a bit high, ~40:1. Plugs are very dark and wet. Both cylinders are the same.
Working through hints from TTY site and the service manual I have disassembled and cleaned the carbs at least 3 times. I did find the needles at 1 and 1.5, both are now set to 2 but nothing plugged or out of spec. O-rings and gaskets in the carb have been replaced as well as the needle inlet valves. Float height measures fine and all jets are stock (per markings). Have also replaced fuel filter and adjusted the oil pump. Inspected/cleaned choke linkages, they are free and appear to be seating fully.
Was able to get out yesterday (temp in 20s). Started out with fresh plugs gapped to 0.030, performance was improved from last time out but still not right. After 40-50 mi sled began to start harder (crack throttle), idle was rough and WOT was down. Road 120 mi on the day, should have changed plugs mid way thru the day but didn't. Suspect a fresh set of plugs would have got me back to where I started the day.
I'm beginning to think that the poor performance might be more of an electrical problem than carburation. First steps will be to measure plug cap and coil resistances.
Options:
1) rebuild carb with new jets?
2) rebuild fuel pump?
3) replace oil pump?
4) look into magneto/stator?
Any thoughts on where I should head with this? The sled is in nice shape mechanically but mid-range performance is really important to enjoying the ride. I've been around sleds most of my 50+ years but am a novice in the finer aspects of engine tuning and this level of repair.
Thank you!
Hank
Sled idles fine and runs ok at WOT but has extremely poor mid-range (3/4 throttle to run 30 mph). Gas mileage is poor at 6+ mpg and oil usage is a bit high, ~40:1. Plugs are very dark and wet. Both cylinders are the same.
Working through hints from TTY site and the service manual I have disassembled and cleaned the carbs at least 3 times. I did find the needles at 1 and 1.5, both are now set to 2 but nothing plugged or out of spec. O-rings and gaskets in the carb have been replaced as well as the needle inlet valves. Float height measures fine and all jets are stock (per markings). Have also replaced fuel filter and adjusted the oil pump. Inspected/cleaned choke linkages, they are free and appear to be seating fully.
Was able to get out yesterday (temp in 20s). Started out with fresh plugs gapped to 0.030, performance was improved from last time out but still not right. After 40-50 mi sled began to start harder (crack throttle), idle was rough and WOT was down. Road 120 mi on the day, should have changed plugs mid way thru the day but didn't. Suspect a fresh set of plugs would have got me back to where I started the day.
I'm beginning to think that the poor performance might be more of an electrical problem than carburation. First steps will be to measure plug cap and coil resistances.
Options:
1) rebuild carb with new jets?
2) rebuild fuel pump?
3) replace oil pump?
4) look into magneto/stator?
Any thoughts on where I should head with this? The sled is in nice shape mechanically but mid-range performance is really important to enjoying the ride. I've been around sleds most of my 50+ years but am a novice in the finer aspects of engine tuning and this level of repair.
Thank you!
Hank
A couple of bucks
VIP Member
BornYamaha
Member
Just also make sure the clutches are back shifting properly with a decent belt. These sleds have decent top end power for a 500 but are very peaky with not much midrange. Your mpg is not that uncommon unfortunetly.
A couple of bucks
VIP Member
Any idea of why the P/O was dumping so much fuel in at the 1.0 & 1.5 settings? A setting of 2 is a step in right direction. The plugs will tell you when to stop 'dropping the cork".
I still have these two reed stoppers as the guy never got back to me. Makes for snappier mid-range. Post #20.
https://totallyamaha.net/showthread...h-question-for-99-Venture-500?highlight=Goose
Alright, I wasn't even aware that the plug caps unscrewed from the plug wires...
I'm not able to take it out for a test but I removed/reattached the caps, dropped in another set of plugs and there is a noticeably different sound to the engine at 1/4 throttle. I'll get a couple of stock replacements on order and see where that takes me.
The needles were "moved" prior to my buying the sled, I'm just trying to get back to stock as this is my spare sled used by my daughters when they can join me.
I owned this exact model back in the early 2000s so have a good idea on what the sled should feel like when right.
Thanks again!
-Hank
A couple of bucks
VIP Member
The stock clip position is in the 2 spot. You can easily move them to the 2.5 safely.
Use dikes and Vaseline.
https://totallyamaha.net/showthread.php/93790-Iridium-spark-plugs-in-a-redhead?highlight=TB05EM
NGK plug caps #TB05EM or TB05EMA can be had at most any Motorsports dealer reguardless of make.
Use dikes and Vaseline.
https://totallyamaha.net/showthread.php/93790-Iridium-spark-plugs-in-a-redhead?highlight=TB05EM
NGK plug caps #TB05EM or TB05EMA can be had at most any Motorsports dealer reguardless of make.
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A couple of bucks
VIP Member
As far as the needle & clip position, think of them as a cork. The further down in the carb they are, the less fuel will flow. Similar to a cork in a bottle. The further the cork is in the bottle, the less wine will flow.
A couple of bucks
VIP Member
I have supplemented coil wires w/ plain 'old black rubber fuel tubing. Just unscrew the plug cap and slide appropriately sized black rubber fuel hose all the way to the coil. It's nice and thick. Pretty much guaranteed to never let stray voltage get to ground. At least not in our lifetime.
Some Vaseline helps the sliding.
https://totallyamaha.net/showthread.php/93790-Iridium-spark-plugs-in-a-redhead?highlight=TB05EMA
Some Vaseline helps the sliding.
https://totallyamaha.net/showthread.php/93790-Iridium-spark-plugs-in-a-redhead?highlight=TB05EMA
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Hey "couple of bucks",
Wanted to say thanks for the tip!! Ohm'd the plug caps, one was 5.2k but the other was 300k+
Clipped the plug wires back 1/2" and installed the new caps and have significant difference in the sound at idle and throttle response on a stand.
The Vmax was definitely running on less than 2 cylinders, I don't live in a spot where I can take a test run but am hopeful this is the ticket.
Thanks again
Hank
Wanted to say thanks for the tip!! Ohm'd the plug caps, one was 5.2k but the other was 300k+
Clipped the plug wires back 1/2" and installed the new caps and have significant difference in the sound at idle and throttle response on a stand.
The Vmax was definitely running on less than 2 cylinders, I don't live in a spot where I can take a test run but am hopeful this is the ticket.
Thanks again
Hank
A couple of bucks
VIP Member
And those numbers are taken when cold. Once they are warm/hot, those numbers would be even worse.