My Vf1000 frustrations

Another update.

The carbs I have been using were the ones from my original motor as I know they work. Today I spent some time cleaning up the old ones that came with the motor. I checked all the diaphrams for cracks and splits and cleaned out the float bowls. I then fitted them to the motor.

Once fuel got through it fired up the same as before but STILL HAD THE SAME PROBLEM OF NOT REVING PAST ABOUT 3000 RPM. There is no discernable difference in the way it runs.

I think this eliminates the carbs. I doubt both have exactly the same problem. What are the chances of that? I was also using fresh fuel.

I am now suspecting either the fuel pump or soemthing like the CDI units or even the fuel filter. Something must be restricting it from reving higher like a lack of fuel.

I haven't been able to get a compression tester that fits. I brought two. One with screw in fittings that weren't the right size and a push in one that wasn't long enough to reach the plug hole. I returned both of them, none the wiser on the compression issue.

This is definitely an ongoing project, or a dump it and move on project.

 

I would still take the carbs apart and clean out the main and pilot jets - you mentioned this has gone on for months - gas will gum these parts up after a couple months, and it's very possible both sets of carbs have the same prob because you don't know how long gas sat in the new carbs before you bought the motor. A pinched gas tank vent line could also prevent the motor from reving past 3,000 but it wouldnt explain the lack of heat/color of the #3 cylinder and plug...I think that would require 2 things going wrong.
Do you still have the old motor? you could try swapping the heads, which would eliminate the possibility of bad valves on the #3 cylinder. Also I'm sure youve done this but make double sure the right plug wires are going to the right cylinders. Not sure what else to suggest, good luck.

 

As Nailer45 suggested, have you checked fuel really is getting to carbs at correct pressure? I have only just sorted my FG with almost exactly the same symptoms as yours. Does the VF1000F have a fuel pump relay? If so, have you bypassed it? Have you checked the fuel tap is done up tightly and seals correctly? The strange 3 hole rubber seal behind the tap - if the tap is the same as the FG, which it sounds like it is from your description, can leak if not fully seated and sealed. Seal with a thin layer of silicon? These taps are 1/3 way up the tank, meaning a siphoning effect is needed to get fuel out when fuel is below 1/3 full. Fuel pump really has to suck! Is the fuel filter new? I presume there is one between tank and fuel pump. To be honest, I'm not sure whether it was the tap leaking, a partially blocked filter or the fuel pump relay that was the cause of my problem - but sorting all 3 has certainly brought my FG back to full health! Good luck! Regards, Tom

 

Further thoughts for you Techno:
Just found an old VF1000 Clymer manual on my bookshelf! I had a VF750 briefly years ago. Fuel pump relays are notorious on these models - they take their switching signal from the ignition circuit, not a simple DC on/off voltage. They get a pulsed DC voltage - exactly the same as that which goes to the low voltage ignition coils and tachometer. Heaven knows how it triggers the relay! They appear to be solid-state and are all sealed up in resin. The fuel pump relay can get confused at higher revs when they start to fail - it works fine at low revs and then fails higher up. Result, fuel pump switched off at higher revs! Solution: find fuel pump relay - just to the right of the regulator. Its the small rectangular fella in a rubber mounting bracket on an electrical panel. It has a 3 pin connector. Unplug connector and push in a shorting strip of wire into the plug connecting the black and the white wire. Bind with insulating tape to secure. The 3rd, blue wire is the trigger line that goes to ignition coil - for No3 cylinder would you believe?! Connected with misfire? Leave that connection alone and leave the relay completely out of circuit. You don't really need them - just a safety device so fuel isn't still pumped if engine stops in a crash. The pump will now come on with ignition switch and not have to have the engine running. It should now pump healthily fully up the rev range. If it doesn't, suspect the pump. Connect a fuel pipe to outlet of pump and see how fast it pumps fuel out of your tank into a container when switched on. Manual says 900cc per minute. If you want the manual for the price of postage, you're most welcome. It's over 400 pages, American and covers Interceptors 700-1000 1983-1985.
Don't give up! Regards, Tom

 

Well the mystery remains.

I took the fuel pump relay to an auto electrician to see if I could get another to eliminate it as the cause. He didn't think it was the relay. We had a chat about it but everything he suggested I had pretty much already tried.

I tried Tom's suggestion for wiring it without the relay. the pump ran fine. I then ran it with the motor running but with no relay and the wiring loop in place and it still had the same problem. I didn't get to measure the flow rate but I think its getting plenty of fuel.

I read somewhere that the rev limiter is in the tacho. I had previously removed the fuse for the instruments and it made no difference. After talking to the auto sparky I decided to pull the plugs on the instruments altogether in case the rev limited was still in circuit. You guessed it. No difference.

The only things I haven't changed are the CDI units as I don't have any spares. I know there is a VF1000 at a wreckers about 200km away. The guys there are reasonable and I'm thinking of getting them up on the basis that I can return them if it makes no difference.

In summary:
- I really don't think its the carbs. I have exactly the same problem with two sets and its too much of a coincidence.
- fuel supply seems good and it should have enough fuel in the bowls to keep going even if it is blocked further up the line.
- its not the coils as I have changed them with no difference.

I don't want to admit defeat but I think I'm staring at it right here.:frown:

 

Well from reading all this, I would suggest checking the magnetic pick ups on the crank (with an ohmmeter) if they check out good then the only thing you have left is either the wiring itself, or the CDI. and if you have a wrecker nearby that had one I would go ahead and get it because parts for that bike are becoming hard to come by anyway. If you need a wiring diagram for that bike let me know and I can see if I have the one for mine and scan it off, and send it to you.

 

advise check valve timing. you may have more than one prob , and your
description of symptoms mirrors perfectly an experience i had , turned out to be valve timing .

 

Just another update.

Having thoroughly exhausted my mechanical skills, I have given the bike over to a pro to diagnose.

As I live in an area with a relatively small population there aren't many choices of bike mechanics. I don't have much confidence in many of them as I have had them do work before and could have done it better myself. The guy who has it now has my conifdence so far.

He will get back to me in the next few days and tell me if he can find whats wrong and if so, whether its worth fixing or not. I'll report back for the sake of closure and to satisfy the collective curiosity. Either way it will no longer be sitting in the garage taking up space.

 

here's a wiring diagram I said I had if you need it

i'd shrink it down but then it wouldn't be as good

 

Well, just to round out the topic.....

I spoke to the mechanic today and he can't cure it either. After taking up room in my garage for two years I am calling it quits and moving on.

I will pick it up on Thursday. I'll then see what the local wreckers will offer me and consider whether its worth selling it whole or parting it out.

Another old bike bites the dust... as much as I hate admitting defeat.:frown:

 

Before you give up on it , try 1 more thing...take the gas tank off and remove the float assembly and the gas on off assembly..take a air hose and blow low pressure through the holes where the gas on off was and see if you can blow out any debris.. the vent on the tank could also be partially blocked causing it to cough and die...
The website www.VFRdiscussion.com has 2 members that are owners of VF1000F and more than likely could tell you what it is that keeps the VF running past 3,000rpm..Just start a thread and ask for help..

 

Thanks for the advice.

I've already tried running it with fuel coming from another source other than the tank. I was trying to eliminate the tank as the source of the problem. I found out that its not. I could keep trying for years and still not get it to run right. Thats time I could spend riding.

Anyone need any parts?

 

actually yes.. I do need parts....

Fuel tank and front faring, and side fairings if you bike has them. How much, and what do you think it would cost to ship stuff to Kansas,usa? If you have pics it would help.


Actually I just had an idea.... sounds kinda simple but try reversing the firing order on the coils... even if you have the coils wired like they were when you started try them in a different order, perhaps the 85 uses a slightly different setup, try changing the coil wires from cly to cly to see if the fireing order is different. if you do have it off to begin with it would cause the backfiring and the bike would still run at low RPM and would only have problems when you reved it to about 3 grand. their verry fickel motors and timing is a big issue with 4 cams and 2 coils... perhaps you just got two wires on the same coil going to the wrong side of the engine or something simple like that.. whatever the problem.. Let me know whatever you deside. But try this first. it won't take long and it's free to test.

 

Just curious, did the mechanic do a compression and leak down test on each cylinder?

 

Techno - I'm sorry to hear you have reached the boiling point with the old girl...

The internet can be a tremendous resource for repair advice, but it has a limit - no one here can see / hear / touch this bike. Mechanics absorb tremendous amounts of information just through observation, without ever touching a tool. I've been repairing them for my living for 22 years now, so stories like this frustrate me. If only I could get ahold of this bike!

One thing I can iron clad tell you though - there is no such thing as an unrepairable bike. It doesn't make economic sense, sometimes (in fact, a lot of the time) but it's never impossible.

If the mechanic who looked at it can't figure it out, try another mechanic. Then you can make an informed decision.

 

been following along and saw you said the spark weakened when you rev'ed it up. did you go through and check the pulser coil for Voltage(.1 to 3VAC) and resistance(don't know spec)? alsovoltage to your brain box(not sure the system TPI or DC-CDI) and the brains grounded to chassis. if your carbs are "good" and your coils are "good" and even if compression is a little low then it would still run, just crappy. but the fact that it "spurtters" at 3 grandish and you have tried and tested the fuel system all thats left is spark. don't give up you'll regret it trust me.

 

Sounds electrical to me... especially w/the weak spark... This has to be something over looked...

 

After reconsidering I think it's actually low compression - the thing ran ok before he bought the used engine, hell he's tried everything else!

 

New guy here - but been reading and messing with V-4's for about 9 years.

The only thing you changed was the engine. It's probably the engine.

Here are my suggestions . . .
- Definitely get a compression check done - as was said before, low compression could be a cause

- Sometimes when cams are re-installed, they are put back in 180 degrees out of phase. The bike will run, but it will stumble when it hits around 5-6K. I know you said your stumble is around 3K - and you have checked the timing already - but many engine rebuilders miss this.

- When running, spray WD-40 around the carb boots. If there is an air leak, the RPMS will change.

- As far as the #3 carb, after running the bike, shut it down and attach tubing to the drain nipple on the underside of the carb. Unscrew the drain screw and see if any fuel is coming out. Compare the amount to one of the other carbs - they should be approx. the same


At what throttle position does the bog down occur - 1/4, 1/2, 3/4, WO?
This will tell you what fuel circuit is being used in the carb.