1983 VF750F Resto

Allyance,

She has some nice looking upgrades on her already though, did you do anything to your suspension?

-Arrmon

 

Installed the new fuel tubes, Bench synced the carbs because I found one cylinder to be open 1/8" more than the others. Now she's not running so good. I used a thick piece of paper to set the throttle plate openings roughly equal. Wedged the whole job back on the bike, fired her up. She start up ONLY with choke, the bike will not start or run with the choke off, even more so with throttle. Now if I turn the choke all the way on, it will spool up to 3000rpm. If I get the bike idling at lets say 1000 rpm and I touch the choke the bike dies. Right there, done. But If I use the choke to spool the bike up to 3000, I can use the throttle to rev the thing all over the place.

I'm thinking I had some cobbled AFR for idle before I balanced the throttle plates. I think the bike is running lean at idle, because adding extra air is killing it. I'm going to try playing with the pilot screws to get her to idle nice and come off the line well. Out is rich on this bike correct?

 

adjust your pilot screws out 2 1/2 to 3 turns. make sure all your rubber manifolds are tight.

 

Check your float levels as well.


cheers

 

She has a FOX shock, which I bought in 1985.

 

Grey,

I'll fiddle withe the pilot screws like planned. Do you think if I sprayed ether/gasoline into the air around the boots I could check for leaks? see if the engine reacts?

Sauceman,

I didn't open up the carbs, so the floats should be where I left them. I'll take a look if I have to pull the carbs again.


-Arrmon

 

I think the idle screws on those early V4 carbs are for the air bypass...but I'm not sure. My guess is that out is leaner, in is richer. If it's only running on choke you're idling pretty lean. You're so close though, considering all you've been through already.

The last time I had this problem on a V4 it was leaned out due to plugged idle jets. I thought they were clean, but they weren't. In the end I needed to drill them out with a pin vice. I'm not sure what the smaller carbs run...a #38 jet? That'd be something like an 0.40mm bore IIRC.

Trust me, I feel your pain, but I'd be pulling the carbs one more time to check those idle jets, air bleed passages, diaphragm seating, float level, throttle plate sync, etc.

I'd also suspect internal cracks on the rubber boots...I usually seal mine up with a thin coating of silicone grease like NAPA Sil Glyde.

 

The grease would have helped, it was loose carb boots. A quick spray on any cylinder boot gave a 1krpm jump. So I spun them down until the clamps were solid. And then I took it for a quick spin:triumphant:

Speedo cable is MIA, Idle was bouncing between 2-4. settled on four after a while. That made for a super uncomfortable ride back up my gravel driveway. But hey, once she cools down I'll wedge my hand in there and bring that down.

So I should be on the road for Memorial day!

 

Ok,

So I've had her out 4-5 times this weekend, and whenever I get on her hard she blows coolant out the radiator cap. I pretty much gotta keep her under 6k to keep me dry . I put a new cap on part #7516 from autozone. No difference. Any clues as to what could cause this overpressure? I'm at a loss. Oh, and the temp has never gotten to the H on the gauge, but it does rest in the 1/2 to 3/4 position while I'm riding her.

-Arrmon

 

I've had bad caps before, and pressure leaks from radiators. Weak o-rings in the coolant pipes at the cyl heads and blown water pump pressure seals are typical. If any part of the system won't hold 13psi it'll definitely boil over. OTOH if you have a blown head gasket or cracked head, no radiator cap will hold the pressure. The last V4 I bought had a blown rear head gasket.

See if you can't beg/borrow/steal a pressure tester. I bought one a while back and it's an incredibly useful tool for tracking down coolant pressure leaks. Some auto stores will have free rentals. Just drain the system, pump it up to the correct pressure with the bayonet neck adapter, and see if it'll hold pressure for an hour or so. Then test the cap. You'll have an answer either way. The only trouble I've had with mine was that it doesn't generate enough pressure to hear leaks. Alternatively, you could use a compression tester or a leakdown tester to see if the cylinders and heads are OK.

 

I ran a compression test previously, most cylinders were within 1-2 psi of 168, the Right front was at 172. I know that's a few pounds low but it's not too bad. I would think I wouldn't have any compression at all with a head gasket leak? Or at least it would fall rapidly. I'm going to go through the overflow tank and vents tonight. I thought it would go from the radiator, into the overflow and out the vent tube if anything were to over pressurize. I'll give the local autozone a call about the pressure tester. I think I can shine a light in the dipstick tube and look for water in the oil too.

-Arrmon

 

Instruments back on, headlight in, fitting new (to me) front cowl after relieving bottom for Lockhart oil cooler.

Ending up replacing just about anything rubber, O-rings, gaskets, dust covers, clutch & front brake master kits. This is getting expensive!

 

Ally,

Could you send me the link of where you bought the rubbers?

And I've made some headway on the coolant. I filed the radiator cap tangs/flanges down so it fit better and folded them in towards the cap so it held the radiator tighter. It reduced the coolant volcano to a coolant dribble. I dried off the cap and radiator and applied a thin layer of silicone to the radiator and put the cap back on. I will go for a ride tonight and see what I get.

-Arrmon

 

Partzilla has all the Honda OEM rubber parts, everything else is hard to get.