85 Vmax will only run with Choke

VMAX  Forum

Help Support VMAX Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

stobrien

Member
Joined
Oct 23, 2016
Messages
24
Reaction score
0
Location
Calgary
I just purchased an 85. I got a good deal, and now I must deal with a few issues that I could use some help on.

1. The Bike will start with full choke on and stay running after running for 10 or 15 minutes it will idle without the choke but dies when you give it any throttle.

According to the past owner The fuel pump is new and the carbs have been flushed. What ever that means.


2. The seat has cracked I would like a simple basic cover.


I would love to send the carbs to someone but I live in Calgary, Alberta Canada so there are some challenges with the boarder and additional cost. I am trying to keep my cost down.
 
Cheapest option is to go thru the carbs yourself.
Check out the carb section of the forum.
It has all the info you need to take them off the bike, clean them up, set the floats, and synch. If you have more time than money, it is your best option.

Remove carbs. This thread is directed at main jet replacement but Mark did a great job of detailing how to remove the carbs easily.
http://vmaxforum.net/showthread.php?t=3570
Rebuild
http://vmaxforum.net/showthread.php?t=5830
Set Floats
http://vmaxforum.net/showthread.php?t=1427
Check the floats after they are set
http://vmaxforum.net/showthread.php?t=17274
Synch
http://vmaxforum.net/showthread.php?t=3959
Might as well check the vboost cable while you are at it
http://vmaxforum.net/showthread.php?t=4361

As far as the seat goes, a local upholstery shop could repair. Sean Morley can fix you up but that requires shipping to US. Or, you can buy a whole new cover from ebay.

Another option would be a want ad for a used seat in good shape. Sometimes they go for a reasonable price.
 
As with any 'new to you' bike I would start by giving the bike a full service - checklist here and colour Service Manual here.

Change all filters, oil, plugs and if they look original the HT leads and caps.

Also don't take the PO at face value and check the work they say they have done.

I'd also run come carb cleaner through the fuel system before pulling the carbs apart although as you say the bike will tick-over without the choke it would suggest that the idle jets aren't blocked.

My next step would be to inspect the carb. slide diaphragm's for any leaks.
 
As with any 'new to you' bike I would start by giving the bike a full service - checklist here and colour Service Manual here.

Change all filters, oil, plugs and if they look original the HT leads and caps.

Also don't take the PO at face value and check the work they say they have done.

I'd also run come carb cleaner through the fuel system before pulling the carbs apart although as you say the bike will tick-over without the choke it would suggest that the idle jets aren't blocked.

My next step would be to inspect the carb. slide diaphragm's for any leaks.

+1, You can spray carb cleaner right into the vents to get it into the pilot jets. That's what I like to do. You can add your favorite carb cleaner in the gas tank too.
Start Your Engines- is some powerful stuff for crud break up. Seafoam is good too.
Steve-o
 
If the bike will only run with the choke on, it sounds like its time for a shotgun. That is a quick way to clean the idle circuits, and its very easy to do.

http://vmax.lvlhead.com/tips/shotgun.htm

This is a good start. One (or more) of your jets is plugged so you will need to do some carb work if the shotgun doesn't work. The cost involved in either sending it to Dannymax or one2dmax will be well worth it. The carbs will come back like new. Both are Vendors on the forum and have excellent reputations.
 
One (or more) of your jets is plugged so you will need to do some carb work if the shotgun doesn't work.

Perhaps some clarification is needed? The title of the post does say '...will only run with Choke' but in the body of the post Mr Stobrien says:

The Bike will start with full choke on and stay running after running for 10 or 15 minutes it will idle without the choke but dies when you give it any throttle.

If the idle circuit(s) were blocked then I would have thought it would have an erratic idle or the headers of the affected cylinder(s) would be noticeably cooler. I would also have expected it to accept some throttle once the needles kick in.

One final thought - can we take it as read Mr Stobrien that the cabs have been synchronised?
 
Perhaps some clarification is needed? The title of the post does say '...will only run with Choke' but in the body of the post Mr Stobrien says:



If the idle circuit(s) were blocked then I would have thought it would have an erratic idle or the headers of the affected cylinder(s) would be noticeably cooler. I would also have expected it to accept some throttle once the needles kick in.

One final thought - can we take it as read Mr Stobrien that the cabs have been synchronised?

Yes I'll admit I didn't read that part of his post. I'm still suspecting one of the jets is plugged, perhaps the main jet. We really need one of our carb gurus here as it has been too long since I've worked on the carbs. I think a damaged diaphragm may cause the same issue.
 
found a few new discoveries.

Has anyone ever heard of an 85 that came without VBoost. It is not there and there are straight pipes between the carb intakes.

It also seems my 2 front cylinders are not firing. Any direction where I should start investigating.
 
found a few new discoveries.

Has anyone ever heard of an 85 that came without VBoost. It is not there and there are straight pipes between the carb intakes.

It also seems my 2 front cylinders are not firing. Any direction where I should start investigating.

Thats part of a stage 7 kit. What exhaust to you have stock or aftermarket? When I mentioned the shotgun, when you pull the slides out........look at the needles. Stage 7 needs are the 2nd from the left. Stage 7 kits have different jets......etc.
 

Attachments

  • FP needles.JPG
    FP needles.JPG
    41.5 KB · Views: 9
Thank you that explains things.

I'll be doing the Shot Gun next week.

It has stock pipes. Can a stage 7 kit run with stock pipes?
 
Thank you that explains things.

I'll be doing the Shot Gun next week.

It has stock pipes. Can a stage 7 kit run with stock pipes?

Yes it will.....but will run worse than the stock set up. If it is a true stage 7 kit, it will need an aftermarket exhaust......so FIRST, find out if it is a stage 7 kit, and report back here what you find.
 
Thank you that explains things.

I'll be doing the Shot Gun next week.

It has stock pipes. Can a stage 7 kit run with stock pipes?

Someone told me it is rare for a main jet to clog-more than likely it is a paj.
Also check if there is spark in the front 2 spark plug as 2 cylindres going out at the same times leans towards a faulty ignition box.
 
found a few new discoveries.

Has anyone ever heard of an 85 that came without VBoost. It is not there and there are straight pipes between the carb intakes.

It also seems my 2 front cylinders are not firing. Any direction where I should start investigating.

If you have the front and rear intakes connected by the open pipes how have you balanced the carbs.

You need to ensure that the basic set-up is correct before doing (say) the Shotgun.

You also say the front two are not firing; are you getting a spark there?
If not then you need to check the relevant pick-up coil.
 
I think this might be a really bad synch issue, too. I had this problem (won't take throttle) on one of mine when I was reviving it. I did basically a bench synch on the bike using a strand of wire to set all the butterflies. I bet if you look down into the tops of your carbs, all the flies will be open different amounts.

You might still have some minor clogging issues, but this should help iron out whether it's a spark or synch problem. Running on two cylinders sounds really wrong on a Vmax. Post a video if you can.
 
Yes it will.....but will run worse than the stock set up. If it is a true stage 7 kit, it will need an aftermarket exhaust......so FIRST, find out if it is a stage 7 kit, and report back here what you find.

It does have a stage 7 kit. I'm on a tight budget. should I remove the stage 7 or try and find a less expensive exhaust?
 
It does have a stage 7 kit. I'm on a tight budget. should I remove the stage 7 or try and find a less expensive exhaust?

Ok, if your on a tight budget (because the V-boost mechanism is expensive....even used, and airbox is 50+ dollars...plus odds and ends)

Used Vboost http://www.ebay.com/itm/91-Yamaha-V...ash=item4b0db941a9:g:StgAAOSwcUBYSG69&vxp=mtr

If the controller doesnt work....that is usually 100.00 USED...etc.

So For the sake of money, I would suggest jetting, etc, and then get an aftermarket exhaust. You can probably jet leaner and help with mileage....etc, until you can do the exhaust.

A good used aftermarket exhaust is probably 300-500.

So when the bike is running on all 4 cylinders, how is the mileage?
 
IMHO until you are able to correctly balance the carbs any other mods will be a waste of money.
If you don't want to go the full V Boost route then just fit the butterflies that when closed will allow you to balance the carbs. They can then be fixed in the open position thereafter.

Only once you have the basic set-up right would investment in tuning parts make any sense.
 
True......so the carbs will need to be balanced or sync'd. How are the carbs sync'd without having the Vboost? That has to be closed to beable to sync the carbs, and this sounds like a true stage 7 bike, with the vboost elimination tubes?
 
Something like a carb airflow meter like this?

The downside is that you have to measure the depression in one carb at a time but it is probably cheaper than V Boost butterflies.
 

Latest posts

Back
Top