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Old 04-12-2009, 08:17 PM   #1
webbie89
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Default New to the V45; have a few questions.

Hey all,

So I've been a big fan of the Honda V4's since a friend of mine turned me onto them with his Magna. Last week I finally picked up one of my own. Here's the dig:

-1983 VF750
-14,000 miles
-Stored for a few years indoors
-Absolutely babied by its previous owner: Nothing but Amsoil, started regularly while stored, etc, etc.

I've given her the once-over (carbs, plugs, spit n' polish), and until today she started and ran exceptionally well, save for a slightly rough idle (old gas, still need to sync the carbs).

This afternoon I went ahead and drained the old, stabil-filled gasoline from the tanks and filled her up, but my fuel pump decided it wasn't going to kick in. Result: No start-up. I verified that the pump works when connected directly to a 12v battery. I also got 11.5v across the leads in the plug for the pump with the key on. But with the pump connected to the plug, I get nothing.

I figured it unlikely that my bike would overturn the notion that electricity actually follows rules, so I kept investigating. I found that if I bypass the fuel pump relay with a length of wire, the pump comes to life.

I haven't been able to find any relevant info in my service manual(s), so here's my question. Does this indicate a dud relay, or is there some provision (i.e. the reserve sensor) that somehow also fits into the equation? What I mean is, will the relay get the pump moving whenever the ignition switch is on, or do you need to drain all the way to the reserve tank to get any pumping?

Sorry for the long post, and thanks in advance for any help you might be able to offer. I hate jumping across relays with wire for any length of time if it can be avoided.

Casey
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Old 04-13-2009, 06:35 AM   #2
seruzawa
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I had an 84 VF700 Magna, same era engine. I suggest you get rid of that bike before the tranny blows and the top end fries. I had to do the same thing with the fuel pump after I rebuilt the engine for the second time. It blew the tranny and then a week after I got it back together it blew a rear exhaust valve.

But if you keep it you should search the internet for the oiling fix. I don't have the link any more but if you search you should be able to find a guy who sells an oil bypass kit that reroutes the engine oil to the cams. The stock engine system routes the oil from the sump to the tranny and then to the heads which has led to top end explosions of early V-4s on a regular basis.

There was also an upgraded tranny gear sold by Honda later because of the many lunched trannies in the early V-4s.

Probably the most difficult engine to work on ever devised. Good luck with it. I'm not exaggerating here. That old V-4 I had was the worst bike I ever owned and that includes old British junk.
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Old 04-13-2009, 07:58 AM   #3
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But, to answer your question, my vote is that you have a bad relay.

However, if you haven't already, make sure you check your fuse block for corrosion and/or bad fuses. I don't think that is the problem, since I think you say you used the pump plug for your bypass power test, but it's a common problem on older bikes.
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Old 04-13-2009, 12:09 PM   #4
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Thanks very much for the replies. I've already started researching the head oiling mods, and I've got some plans in the works to machine my own oil filter collar to route high pressure oil to the cams. In the meantime, I'm trying to keep the RPM's up whenever I run it, and the combination of high quality oil and low miles eases my worries about existing cam pitting.

I'm just a poor college student, so I'm trying to hold onto the bike for as long as I can.

I'll check the fuses just in case, but the bike is exceptionally clean with no corrosion to speak of. I did use the fuel pump relay plug for my bypass test, and the pump kicked in right away when I shorted across the relay plug leads.

I just found it surprising that the pump would always be running even with a positive pressure head from the main fuel tank. However, I guess I'm mistaken.

So just to be clear, if the relay is good, then the pump will be running anytime I have the bike running, correct?
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Old 04-13-2009, 12:35 PM   #5
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Quote:
Originally Posted by webbie89 View Post
So just to be clear, if the relay is good, then the pump will be running anytime I have the bike running, correct?
That is correct.
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Old 04-13-2009, 01:06 PM   #6
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"I'm trying to keep the RPM's up whenever I run it, and the combination of high quality oil and low miles eases my worries about existing cam pitting."

Cam pitting comes mostly from inferior surface hardening of the cam, and has very little ot do with RPM or oiling.
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Old 04-13-2009, 01:28 PM   #7
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I rigged a bypass wire and a toggle switch to run the fuel pump. I also rigged another switch to run the radiator fan constantly when riding in the city. The radiator on those early V-4s was none too big.
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Old 04-13-2009, 04:44 PM   #8
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"Cam pitting comes mostly from inferior surface hardening of the cam, and has very little ot do with RPM or oiling."

I know that's the case on some top ends. I thought that the early v4's suffered even more from the poor cam lubrication at low RPM's though, especially if the valve clearances are out of whack and you wipe your cam lobes dry. I know that the cams were a tad soft as well, so that didn't help the issue. Please correct me if I'm wrong, because it's none too easy machining an oil collar.

Regarding the fuel pump relay- what, then, is it's purpose? It seems a little superfluous if it sends current to the pump whenever the ignition is turned on. Why not just use a switched hot?
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Old 04-13-2009, 08:37 PM   #9
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Quote:
Originally Posted by webbie89 View Post
"Cam pitting comes mostly from inferior surface hardening of the cam, and has very little ot do with RPM or oiling."

I know that's the case on some top ends. I thought that the early v4's suffered even more from the poor cam lubrication at low RPM's though, especially if the valve clearances are out of whack and you wipe your cam lobes dry. I know that the cams were a tad soft as well, so that didn't help the issue. Please correct me if I'm wrong, because it's none too easy machining an oil collar.

Regarding the fuel pump relay- what, then, is it's purpose? It seems a little superfluous if it sends current to the pump whenever the ignition is turned on. Why not just use a switched hot?
The relay's purpose is to reduce the amount of current that the switch itself has to carry.

I'm serious about the guy who has a ready to go oil filter collar. Since he's worked the bugs out of it it's probably safer to use that then try to re-invent the wheel. If you blow the engine it'll cost a lot more than the $250 he wants.
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Old 04-13-2009, 08:58 PM   #10
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Quote:
Originally Posted by webbie89 View Post
Regarding the fuel pump relay- what, then, is it's purpose? It seems a little superfluous if it sends current to the pump whenever the ignition is turned on. Why not just use a switched hot?
Not just when the ignition is on - when the engine is running. I think the idea was, if you crash and happen to say, knock the carbs off and rip the fuel line, you're less likely to die a gruesome, horrible, flaming death if, when the engine died the fuel pump stopped squirting fuel all-over your limp, unconscious body.

You seem a handy bloke - the relay for this thing probably costs $127.38 plus Taxes and Shipping&Fondling charges - It probably wouldn't be too hard for you to ditch that POS and modify the harness to fit a $10 generic encapsulated 30-to-40 amp relay you can obtain from any auto parts store...............
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