The VFR that wasn't but now is.

I will have to do some more verifications this weekend if I don't have to tractor too much.

Long period - 2 min + with almost a stall out if left un-blipped after 2 min.

1. The insulators are still OLD. They seem seated as I used grease and a ratchet strap to install. Thought I verified with inspection mirror and flash light. Worth another look. I will replace those with my new ones once I complete the clean and paint phase or swap them this weekend and take a spin.

2. These carbs are UK and don't seem to have any vacuum componentry that I can tell. Not your standard Cali carbs.

3. 2.5 on the pilots. Maybe a hair more or less 2.6

4. I did purchase a new thermostat because she does not seem to get up to temp very easily. Barely registers after 5 miles that she is heating up. Although it has only been in the low 60's of late.
5. No running problems of record once I installed the air filter, just the elongated use of choke and higher idle revs once warm.

 

I will almost guarantee you have a folded over lip (and accompanying intake leak) on one of your insulators using that method.
Or you downright tore it.

They need to be done by hand and this is the secret weapon. Its a radiator hose tool. That is the perfect angled one. You can find them used, but they are still not "cheap".


If the boots aren't damaged now, get them nice and warm with a heat gun on low. Install the front two first and the rears will seem a mile off. Hook that down in the boot and while applying a little pressure run it around the rear 3rd of the circumference. The carb will hit the tool a bit, but you will get movement. Alternate back and forth between the rear two while maintaining pressure. Once you see both lips of the insulators is starting to envelope the carbs that's when you double down on the pressure. You want to make sure you're not gonna catch and fold in the lip. Sometimes it looks like it's gonna, but then "releases".

"pop" If you don't get that sensation, regardless of method, it's probably not cool.

Stubborn ones (re-used old insulators) you can use a clean 2x4 on edge. Get under the front tank mount and alternate levered pressure between the rear two corners where the air box would mount. This is an advanced move, but has saved my ass MANY times. You don't want to crack your plenum, that's why your using pretty forgiving wood.

I've tried most methods including boots half on - half off. The method described above, with that tool, is 100% effective and fast for me now. Even with old boots.

I am not exaggerating when I say I've done V4 carbs well over 50 times. I can go from tank-on-VFR, jetting change, tank back on in less than 30.

I know you've spent some coin already, but if you wanna set it and forget it, just get some new ones. They almost fall in using the above method and you wonder, "why the fuck didn't I do this from the start?"

 

I am down for good tooling so I will pick up that bad boy. My truck could use that tool as well. 4 new boots await install...mwhahahah

Thanks for the input...as usual.

I did inspect, but my eyesight is going pretty bad with low lighting. Glasses and more lighting before attempting reinstall.

 

It's one of my all time favorite tools now.

And sometimes a folded lip can be not totally apparent. I've taken some off for the first time and been, "huh". The folded lip is now almost molded in it's new "position".

Also after you get the fronts down in, take a moment and reheat the boots. Get down in the "V" and direct some heat from that angle too. You're not gonna damage anything unless you spend too much time in one place.

And don't forget, the boots need to be "clocked" in the right orientation.

 

I will use my heat gun wisely, don't tell my wife about her hair dryer.

 

I did a bad thing and swapped around good front boot for a slightly munched back boot. My logic was that I could easily keep the munched boot from getting worse as it pushes down cleanly vertically in the front position, but I needed a strong clean edge on the rear boot to work over the carb edge. I know the front and rear boots have different part numbers but could not see any interference or reasons not to do this. There are no air leaks and starting and running is excellent, with a stable idle after maybe 30 seconds of choke.

 

86 - 87 they don't

16211-ML7-000

Another change from 87 to 88 I guess.

I've done the exact same thing (switching locations) for the same reason from somebody else's attempts. But I didn't have to contemplate different part numbers.

 

Everything I found says the front and rear insulators are the same PN. 16211ML7920

https://www.cmsnl.com/honda-vfr750f...dmkh_model5581/insulator-carbure_16211ml7920/

And I hope so because that is all I purchased. Same # for 88/89

Fowlers:

INSULATOR, CARBURETOR
Part Number: 16211ML7920
VFR750FJ - CYLINDER HEAD (1) x 4

 

OK good. I thought, "no way". But then again... maybe? Didn't bother me enough to go look. Cool.

 

Well, not sure where I got that idea from then. I actually tried to order some fresh ones from Partzilla and ended up with a set for a VTEC 800. Must have had a major brain fart.

 

i gotta admit that i usually file down, profile and round off the normally square tube ends that go into the boots on my vfr cabs, taking off about 1mm, and it helps alot getting them mounted much easier.

before


after

 

That, is an excellent thought Squirel Man. good idea. Partzilla nor any other NA company have any listing for an 88/89 vfr750, so I had to go UK for parts. Maybe once Honda got into the 90's all of the models were the same, except California smog.

 

born of frustration !

 

First it is the credit card float gauges. Now we have the chamfered carb edge. What other carb secret squirel stuff are you sitting on mate? Do share.

 

^^^ some day

(i have a new way to bench-synch carbs..........)

 

This is a UK bike and parts fiche for 88 UK market

https://www.fowlersparts.co.uk/parts/5050952/vfr750fj-1988-e-mkh/carburetor-1

Shows different part numbers for two pairs of boots.

Also in 30 years of ownership have found carb balancing using a set of 4 vacuum gauges helps with smooth idling.

You balance as two pairs getting each pair even then use third screw to balance the pairs.

 

^^ those are the plenum velocity stacks (at least that is what I call them). I believe Capt and I are talking about the insulators from the head to the carb. Maybe Terry is reffing the above mentioned as well.

 

Nope, I'm just confoosed...

 

On an extremely happy note. CMSNL delivered. Hell yeah! They must have been impressed with my fluid Dutch-speaking that they threw in a hat, key chain, and a poster that I may or may not put up in the moto garage depending on how man cave I want to go. Not sure if she is sexy or weeping for help? Must be a red light gal.

 

Ill say she is weeping for help, she has the same frustrated look on her face that I have dealing with the GSXR lol