1986 VFR750FG / interceptor stalling problem, very strange any help much appreciated

Hi there members i have always wanted one of the first VFR's and was able to find a pretty original one a few weeks ago, which I was hoping to tour spain with in May. As i'm new to the model (previously a transalp) i'm a new user to this forum, but have been busy fettling away at the bike, sorting out problems with the help of this great site and have done the following so far:

(1) oil service;
(2) clutch bleed;
(3) throttle cable (new);
(4) replaced rectifier;
(5) drained tank and carbs;
(5) bypassed fuel pump to gravity feed;
(6) new battery;
(7) flasher relay;
(8) coolant flush;
(9) fitted panniers and top box;
(10) new thermostat;
(11) speedo converted from KMPH to MPH (originally a Jap import to UK).

I say all this because obviously i've invested some time and money in what I hoped would be a very reliable and easy to work on machine. However, very embarrassingly I haven't ridden a mile on her yet! :redface:

When I start the machine up on the centrestand she fires into life and will sit there on idle all day. Also, if I kick her into any gear on the centrestand she revs freely all the way to the max in every gear with the rear wheel in the air (careful now). However, when I take her off the stand and engage gear (whether riding or walking alongside), the bike splutters and dies out every time within seconds. It is as if the bike does not want to run at all with the wheels on the road.

I have considered the following causes:

(1) Gravity feed being insufficient to fuel the bike-I would have suspected this if the bike didn't rev so well in gear on the centrestand or in neutral on the floor. Plus, I have checked the lines to the carbs after she dies and they are full of fuel. The tank is also full and I have used the spare key to open the cap so no vacuum probs either.

(2) Carbs-surely if these were the cause the bike would not rev through the gears on the centrestand?

(3) Spark tested coming to rear plugs.

(4) Sidestand switch-I start it on the centrestand, run it through the gears with the rear wheel spinning, then push it forward. Even when kept level and pushed along the floor for only a few feet, the bike will splutter and stall. At no time is the sidestand touched.

(5) Clutch-working fine when engaging gear.

Has anyone had the same problem, and is able to shed some light on what else I can try? I should probably say, the bike is in very good condition for its age but hasn't been ridden for about three years (dry stored), eventhough she runs fine on the stand.

It's probably something obvious to the knowledgable???? :wink:

Many thanks for all your help in advance, Fergal (Ireland).

 

:welcome:

Good to see you here.

Might be wrong, but it's my belief that a Gen2 bike won't run all proppa like on gravity feed.......

Use OEM fuel pump, guvna', and heed the essential words of W.B. Yates.

 

+1. The internal plumbing of the tank wont let it gravity feed near or below the petcock level. It needs the pump.

 

Thanks for your quick replies fellas. One of the threads I had been referring to was here:

Fuel Pumps? We Don't Need No Stinking Fuel Pumps! [Archive] - Honda VFR Club

I take it that this cannot be correct??

What confuses me, as I said originally, is that is revs all the way to red when not in gear wheels on ground, and in gear when on centrestand. If absence of the fuel pump was the issue, why would it not die when revved in neutral??

Thanks again

 

+2. I have never heard of these running on gravity. test your old pump or find a new. Sorry I just sold my extra.

 

Guess you can't believe every heroic "bodge" job you read/hear about. Feeling much better now have just bought a second hand pump and relay off a really nice guy on ebay for £20 incl p&p (not bad at all if they work!), so will try them out when they arrive and hopefully be able to report back on my first ride!! Should anyone need anything, here is his ad:

HONDA VFR 750 FG 86 FOR BREAKING LOTS OF PARTS ON BIKE on eBay (end time 30-Mar-10 23:22:51 BST)

Thought this similar looking NOS item might also do the trick if i was stuck?:

UC-J7 Fuel Pump - Honda Accord 77-83 / Prelude 83-92 on eBay (end time 22-Mar-10 16:09:01 GMT)

The pump I have is definately dead (no noise even when connected direct to battery), and the relay has had a jumper cable connected at some point by the previous owner.

Seems to me that Honda couldn't get the electrics right in the 80's. I had an 87 transalp with many of the same faults (plus dreaded CDI failures) of this model vfr, none of which were a problem on the 97 model transalp i replaced it with. The later model funnily enough, was built in Italy (not a nation known for great auto sparking) but was leaps and bounds ahead of the earlier japanese made machine in terms of general build quality. What I did like is that they perfected an already good machine and made subtle improvements, rather than rushing out a brand new model every few years for the heck of it. Great bike, but i'm hoping this VFR will be even better especially in the performance and handling stakes. At least second hand parts are cheap and plentiful now-didn't fancy giving Wemoto over £250 for a pump and relay on a bike that cost me less than twice that figure!!

 

There is no load on the engine with it in neutral, or with the rear wheel off the ground. The more load on the engine, the more throttle (fuel) required.