1985 VF700F - Engine will not fire

Hi, I have a 1985 VF700F Interceptor that has been running great all spring. Last week it developed a problem where the engine takes a long time to fire up or sometimes won't fire up at all. I usually have to crank the starter for a good minute or two with the choke on full for it to start running and even then it's a roll of the dice. Sometimes it won't start at all. If I do manage to get it running then there is usually a good chance it will cut out when I'm idling at a stop light and re-starting it once the engine is warm is very difficult.

I've checked the carbs and they are very clean with no obstructions in the jets. I've also replaced the spark plugs (though not the wires) but it hasn't helped. The battery was new last fall and is always on a trickle charger. A mechanic friend of mine seems to think that it has a vacuum leak and I should replace the rubber carburetor boots, but I'm having trouble finding anywhere on the internet to purchase them.

Does anyone have any advice / insight?

 

Can't help you out, but I'll bump the thread by replying. There are some very knowledgeable folks on here. Good luck in getting it sorted.

 

Vac leaks are easy to find if you can keep it running. while it's running, spray carb cleaner all around the carbs and the around the rubber boots. As soon as the cleaner hits the leak, the RPM's will change and it will smooth out for just a second.

If it's your boots, you can either get them from a Honda dealer, or save a few bucks and get them through bikebandit.com like I did.

Have you changed your fuel filter? Less that 5 dollars at Autozone.

 

Fuel or spark, a lack of one or the other (could be both but not likely) is your problem. Run it down from the top of the supply chain.
Are you getting a good spark? Are you getting fuel?

 

hmmm.

So, interesting. LastV4Interceptor, what has you believing its a vacuum leak, and not just a typical FIRE+FUEL+OXYGEN=RUN situation?

I believe 4a15 and Dkiedook are onto the correct path there.

Since you said it *was* operating just fine, and assuming you havent done anything to it recently, I would look at two places first before I did anything else... Fuel Filter, and Air Filter.

Easy tests..

Take out your air filter, and attempt to start it.

No change?

Leave it off, and open your fuel filter housing, remove fuel filter, close up housing, and try to fire it.

No change?

Leave it like that, and check your fuel pump. Power? pull off the hose to the fuel pump, and try to start the bike (the "On" switch in the "OFF" position)

Pumping good?

There, you've just eliminated Air, and Fuel as a possible failure mode. Double check your batterys voltage, and pull each sparkplug, and attempt a start to see if it arcs. If its arcing... youre Fire is working just fine.

Even with a vacuum leak, it should still start. Running, you should notice a hissing sound from the carb area. And just as 4a15 pointed out, get a can of ether or aerosol starter fluid, and spray up near your carbs. If the engine idles up, you got yourself a vacuum leak. Buy new boots, and replace.

 

Ahh, good to see Ghost back and sharing his wisdom!

I remember all the "Ghost says lets learn about...". That was when I first came around to this site.

Back to topic now.

 

Carbs that you "cleaned" 2 or 3 months ago can clog up during periods on non-use if you didn't crack open the bowl drain screws. Many carb problems begin in the fuel tank, so annual flushing and de-rusting is good preventive maintenance.

For good starting, the enrichener circuit pickup tubes must be clear, something that is best determined by slipping a hose over their outer diameter and blowing air into them or by probing a thin (about .12") steel wire in to a depth of about 30 mm. If you neglected this, you may have worked on the carbs, but you didn't clean them.

 

Squirrelman is another guy full of information, but he's much more, ahem... entertaining when he's tied a few on!

All in good fun. And here's a couple pics for you, Squirrel. One I took. The other I did not.

 

Hi all,

I just wanted to bring closure to this issue even though I fixed it about a month ago. I replaced the carburetor boots ($17/ each) and added a new battery for good measure (really good AGM type. Never buying that $40 crap again). I also had to rebuild the starter because I killed it trying to crank it over and over again. The bike has never started and run better than it does right now. It fires right up by barely touching the switch. Thanks as always for your help, advice, and wisdom. This forum kicks ass!

Eric