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Rescuing a '92 VFR750F


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11 hours ago, Cogswell said:

Not sure why the run on VFR petcocks when others remain available

Yeah... but maybe that's an indication of scarcity of good running VFRs.  Plus the VFRs look awesome so who wouldn't want one. 

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For the record, here’s what I have…

 

the petcock itself has been cleaned and works perfectly. 
 

the plastic pickup tube with screen has been completely corroded. 
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All I really need is the pick up tube and a new gasket/o-ring. If I can figure out a good material filament, I can design and 3D print a solution, I think. Just need to rub the two brain cells together for a bit. 

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This design doesn't incorporate a reserve, does it?  Why is the screen critical to operate the bike with a quality fuel filter installed?

 

You would need something to locate the sealing oring and keep it from pushing inward though I guess.  A short section of some correct sized tubing would suffice.

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4 minutes ago, Captain 80s said:

This design doesn't incorporate a reserve, does it?  Why is the screen critical to operate the bike with a quality fuel filter installed?

No reserve.  The tank has sender for fuel level and a "low fuel" sensor.

 

I don't think the screen is critical...  but if there's anything the tank, it does keep it from clogging the valve.  I don't think I'll find the pickup tubes, so I'm just looking at how to prescreen before the valve.  I imagine that on 20 or 30 year old bikes, that plastic is pretty degraded anyway.

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Wow - that tube looks like it sat in battery acid vs gasoline. 

 

Would the fuel filter be in-line outside the tank?  I think Captain 80s is on to something.  Honda's design seems kind of kooky - difficult to service and as you have, prone to failure. 

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5 minutes ago, Cogswell said:

Wow - that tube looks like it sat in battery acid vs gasoline. 

The tank was had a fair amount of sludge at the bottom before I got it cleaned up.  It was all metal flake rust, old gas... some dirt..

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Today was interesting. Got the plenum reattached and got carbs back on. Decided to hook up an IV and give it a go. New battery attached and turned the key… pushed the button. 

 

She fired right up and sat idling. Choke worked no problem. If I so much think about the throttle, she dies. Starts right back up. 
 

I original had the IV connected to the fuel pump. Noticed the fuel pump “pulses”. Should the pump be on constantly? Maybe it’s a bad pump and / or a fuel pressure issue?
 

 

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Pump only pumps when it senses the pressure drops.  Normal for it to click every few seconds at idle.

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Just now, Captain 80s said:

Pump only pumps when it senses the pressure drops.  Normal for it to click every few seconds at idle.

Perfect. That’s what I thought. So I think the pump is fine. 

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56 minutes ago, damionj said:

Today was interesting. Got the plenum reattached and got carbs back on. Decided to hook up an IV and give it a go. New battery attached and turned the key… pushed the button. 

 

She fired right up and sat idling. Choke worked no problem. If I so much think about the throttle, she dies. Starts right back up.

 

Classic problem with clogged petrol passages between pilot jets and carb-venturi. Passages needs to be scrubbed with brushes and PEA-based solvent to remove dried petrol. A lot of times, it becomes plastic and doesn't dissolve again and needs to be mechanically removed. You've probably also have lots of other debris in there like dust and rust. Also soak in ultrasonic cleaner for +8hrs. Finally micro soda-blast to clear out dried petrol flakes and rust.


Then work it in reverse direction. Poke out bleed-holes in carb-venturi with fine copper wires. Then soda-blast from that direction back towards float-bowls.

 

I've done this at least 50x for carbs that have sat for more than 3-months. Spray carb-cleaners no longer work due to removal of chlorinated compounds. So lots of elbow-grease needed to clear entire flow-path of petrol.

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19 minutes ago, DannoXYZ said:

Classic problem with clogged petrol passages between pilot jets and carb-venturi.

Well crap… that doesn’t sound at all like a quick fix so I can ride. 
 

Guess the carbs are coming apart again. Boo. 

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While you're there, might as well replace all rubbers:

 

- float-valves

- float-bowl seals

- screens

- fuel-rail O-rings (replace rails with metal versions if possible)

- slide diaphragms if necessary

 

Many expert mechanics who can rebuild engines with only their teeth and hands tied behind their backs have had to pull carbs 4-5x for ever deeper cleaning before they were factory-fresh. Then bike runs like brand-new off showroom floor. I suggest doing full restoration 1st time around so you don't have to keep on pulling them.

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6 hours ago, damionj said:

Can’t believe my luck! The cheapo tank I got off eBay is way better than the one I had AND it had a great petcock and strainer tube! 
 

Now to get these carbs sorted. 
 

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Will you be using the new tank or just the petcock?

 

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  • 2 weeks later...
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FYI, the OEM VFR750 petcock does include a reserve function--even if it was not enabled on the US-spec bikes.  That's why it has two inlets, and two strainer tubes.  The same Honda part can be used on bikes with and without the reserve switch on the fairing--the selector knobs are different.

 

Ciao,

 

JZH

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7 hours ago, JZH said:

FYI, the OEM VFR750 petcock does include a reserve function--even if it was not enabled on the US-spec bikes. 

That's a fun bit of information.  I was wondering why there were two strainer tubes with no reserve.  It makes sense now.

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  • 4 weeks later...

Hey All!

 

To say I’m excited doesn’t begin to describe it. A couple weeks ago, I sent my carbs off to @squirrelman for some… pro work. Today they arrived and I had them on Vera within 20 minutes of opening the box. 
 

Well… he did amazing work with those old things. Thanks!

 

Now on to the rest of the fixing!
 

 

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I don’t mean to alarm anyone, but VERA moves! 
 


of course, it looks like I have a ground short somewhere or I need a new voltage regulator. That thing was smokin’! Started to melt the connector a little. 
 

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probably not a short to ground, but check stator resistances according to the "bible".

 

 

remove the plug for inspection and probable replacement.  don't replace a regulator until you're sure the stator is putting out the right voltage.

 

do "the drill"

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