Low speed / idle engine miss

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fbnewell

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Need some good advice. And I KNOW this is the place to get it. Very knowledgeable and helpful folks here!

'89 V-Max (my 3rd one), 24K miles, all stock as far as I can tell. Had been sitting a year w/o starting, and only 250 miles in last 3 years. New battery. Drained fuel tank and carbs. "Shotguned" the thing to death. Got it running pretty well, rides very well. Got 36.8 mpg on a little 90-mile run on mostly freeway @ 70-75 mph. Running non-ethanol regular unleaded w/ SeaFoam. Still has a noticeable miss at low rpm. When get it WOT on main jets and V-Boost, runs like a V-Max should. V-Boost does work correctly. Haven't put any gauges on it, but all 4 pipes seem to be getting warm fairly evenly. Am satisfied this last time that everything is pretty clean / clear carb-wise. Installed new A/F adjustment screw kits, 2-3/4 turns out. Trimmed 1/4" off spark plug cables. New plugs, pulled to check spark (all good), and all looked like running a tad rich (was running 3-1/4 turns out) except left front - very clean and clear. Also, cranked engine w/ plug out on each, left front has good compression first rotation, then seems to drop off noticeably. Have not synch'd carbs or tested compression. Have not checked valve clearance. Have seen some YouTube videos of a V-Max w/ engine noise that sounds EXACTLY like mine, but don't know what his diagnosis was. Wanna know what you guys think this could be. Don't want to spend a lot of time & money chasing / changing stuff that won't make a difference. Thanx in advance for any and all feedback.
 
I'd try a good sync. That can make a really big difference, especially at low throttle openings where one butterfly being slightly more closed/open than the others can make a bigger difference than when they're all cranked wide open. Other than that, it sounds like you might still have a bit of junk in your pilot jets.

Post the video of the bike you're talking about, and we'll go from there.

Welcome to the board.
 
What Dave said.

I've become pretty OCD about idle and off idle performance and a regular carb synch really helps keep it happy. I usually throw the Carbtune on it a couple times a season as routine maintenance or anytime I touch the carbs. I do all my own maintenance and repairs, the carbsynch is my most used tool. I got a Carbtune for $110, which was less than the shop wanted to do the job twice so it's paid for itself.

Even a cheap compression gauge will tell you if your consistent between the cylinders, I think Autozone or one of those places has loaners/rentals. IIRC the valve adjustment comes at 30k miles but the bikes been around for nearly 3 decades so if all else fails it might be something to consider.

Even if you cant get a vid of yours maybe you can link the one on youtube that sounds exactly like yours and give us an idea.
 
After a sync, check for air leaks around all the boots. If they are original, they surely are do for a change. They get hard and crack. I needed some valve adjustment at 24k miles. But they weren't drastically out of spec. And, valve adjustment isn't a noise causing issue on our engines usually. The noise? It's hard to tell for me from a video, but possibly there is some chain looseness. Check your adjusters, nothing to loose.
 
What Dave said.

I've become pretty OCD about idle and off idle performance and a regular carb synch really helps keep it happy. I usually throw the Carbtune on it a couple times a season as routine maintenance or anytime I touch the carbs. I do all my own maintenance and repairs, the carbsynch is my most used tool. I got a Carbtune for $110, which was less than the shop wanted to do the job twice so it's paid for itself.

.

Where do you get one of those carbtune tools? Are there any good video tutorials on how to use it?
 
Carbtune can be bought direct from the manufacturer in UK.
http://www.carbtune.com/carbpric.html
They ship faster than you'd think.
Probably be less than $100 due to exchange

Synch is a simple process on the vmax. Here are some instructions.

http://vmaxforum.net/showthread.php?t=3959

http://vmaxforum.net/showthread.php?t=43398

I got mine on Ebay but that was before I learned how fast you can get it from them directly. I have had a few in the past but this one is easily my favorite. You wont regret owning one.
 
Thx, guys. Got a CarbTune Pro 4 ordered this afternoon off Ebay, be here Friday. Will be great for use on my V-Max and my new-to-me '98 Honda Magna. Just rejetted the Magna, will be good to complete the tuning. Checked out the two posts on sync-ing the carbs, looks like really straight-forward. Again, thanks for all your help. Love the forum here. Will get back with you post-sync if that doesn't fix it.
 
If you are going to drive japan carburettor bike you won't regret to have a carb sync tool. Not useful on HD and modern injector bikes. I use one like this myself.
dsc00386-jpg.181547


But it seems the noise in video is not because of of carb sync problem. It's more like an air leaks through a rubber tube under carb, like sdt354 said. 1FK-13597-00-00, 17$ each on boats.net.
 
If you are going to drive japan carburettor bike you won't regret to have a carb sync tool. Not useful on HD and modern injector bikes. I use one like this myself.
dsc00386-jpg.181547


But it seems the noise in video is not because of of carb sync problem. It's more like an air leaks through a rubber tube under carb, like sdt354 said. 1FK-13597-00-00, 17$ each on boats.net.

Lot's of different types of sync tools available. The carb tune is most popular here because of ease of use and size. I"ve got an Edelbrock sync tool also, it works ok. It sits on top of the carburetor. Anything using a hose to the vacuum port should have restrictors in them.
Steve-o
 
If you are going to drive japan carburettor bike you won't regret to have a carb sync tool. Not useful on HD and modern injector bikes. I use one like this myself.
dsc00386-jpg.181547


But it seems the noise in video is not because of of carb sync problem. It's more like an air leaks through a rubber tube under carb, like sdt354 said. 1FK-13597-00-00, 17$ each on boats.net.

+1 for boats.net. I ordered everything to rebuild my Venture forks and some other stuff, all OEM parts and about as cheap as I could find them anywhere.
 
If you lift the clutch does the noise reduce, if it does it's probably noise from clutch/primary drive due to poor carb sink.


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