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1994 vfr750 repairs. Looking for some input


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I wouldn't fret about the holes; forget about them.  Block them with duct tape if you decide to cover them. It's a sign he may have installed A JET KIT.

Correction to your guesses: a bike running too lean will be harder to start in cold weather, while too rich (within limits) is easier starting in cold.

 

 

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1 hour ago, squirrelman said:

I wouldn't fret about the holes; forget about them.  Block them with duct tape if you decide to cover them. It's a sign he may have installed A JET KIT.

Correction to your guesses: a bike running too lean will be harder to start in cold weather, while too rich (within limits) is easier starting in cold.

 

 

 

I am going to block the holes, going to tape and then fill with epoxy. 

 

I know that running rich would make it easier to start when cold but it is the opposite! While one would think this would point to lean, all I can smell is how rich it is at idle (doesn't matter if it's a warm summer day or cold fall day) While not puffing black smoke the rear plugs I removed show it to be rich as heck. 

 

It's been a number of years since I worked on a carb and I'm assuming a bike carb is basically the same as car carb so correct me if I'm wrong. There should be an idle mixture circuit screw and this should be at a set amount of turns out correct? I'm trying to figure out what the writing is (in the pic middle right 2 tabs in top corner of frame). The "mix 1 1/2" makes me think they touched the idle mixture screw and have it at 1 and 1/2 turns out. Like I said I may be reaching but if that is the case does 1.5 turns out increase rich ness? Maybe he was an idiot (after all he did drill the airbox) and thought that increasing the richness with the extra airflow from the airbox would increase power? The other side says origin or something like that so maybe mixture screw was 1 1/2 turns out originally in case them screwing around with it didn't work? 

 

I may be looking too far in to this. I HATE when people fuck around with things that they have no god damn clue how it works or why it is a certain way. A few of the carbed mustangs I owned before had problems similar to this where the PO thought they were "improving something" but really they were making things worse and then screwed around with other settings until what they first started screwing with worked (basically idled and didn't back fire lol). 4 carbs is also a lot more complex than a single non vac assisted 4 barrel lol

 

 

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9 hours ago, NateV8 said:

 

. I HATE when people fuck around with things that they have no god damn clue how it works or why it is a certain way. 

 

 

 

 

Sounds like my last place of work.....  :goofy:

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I have bought a number of used V4's over the years and have found some botch jobs when it comes to carb and airbox modifications. 

 

Since you suspect its running rich and have some experience with carbs, I would recommend the following.

 

1. Identify you have the right carbs. Might as well start at the beginning. 2 bikes I bought had the wrong carbs in them, one was even 2mm smaller on the inlet than oem and they still managed to fit the them. In Canada you should have VP35A's. You can find the stamp just above the float bowl gasket, probably the right side is easiest to see.

 

2. Verify your jet size. You should have 125's. I have seen a lot of screw ups over the years from 6 sizes to big, 2 sizes to small, front and rears swapped to 2 different sizes when all 4 should be the same. All these bikes ran like crap if they even started. I have not pulled a float bowl on my 4th gen while in the bike as I just pulled the carbs for a clean. I have though on my V65 Sabre, V45 Interceptor and both VF1000R's. It can be a b****, but if you can pull one and verify you have the right jets you should be good. You'll need a 7mm socket for the jet.

 

3. Good call covering the holes. They aren't helping the bike run better. I have brought all my bikes back to oem as far as airbox and carbs go. Even with K&N filters in all but 2 and lots of aftermarket cans, they all run just fine and the plugs look good. If the carbs are right, try running the bike with the stock airbox and see how it goes. Then if you want to take the snorkels off, let the bike sit for a day then try starting it from cold and running it on the road. That way you will have a base line as far as any difference in performance.

 

I'm posting a page out of my  Clymers with the carb specs for reference and for laughs what the airbox cover looked like on one of my VF1000R's when I took the tank off. Guess I should thank the guy as it ran so bad when when I tried to take it for a spin that I got it for $500 less than he was asking. Put a proper cover on and oem jets, new tires and serviced the usual, and rode it 7800 miles to Calf. and back without a hitch.

 

When you can, spend an hour or so checking the rest of the bike over. Over the years I've found an axle nut and caliper bolt that I easily removed by hand, a bolt on the shock missing its nut and had stared to back out, a front tire put on backwards, a fork with no spacer....................you get the drift.

 

Good luck with your project.

 

 

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DSCF3281.JPG

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Interesting, very interesting. Thank you for that. 

 

Seeing the turns on the pilot screw (idle mixture circuit?) now confirms what I thought. I bet he didn't notice the difference between 1 1/2 turn and 1 3/8th so he wrote "mix 1 1/2 origin" on the tabs to remember.  

 

In is richer and out is leaner? or vice versa. I can't remember if the pilot limits air or fuel.

 

Until I can get to the bike on sunday I can only speculate what he did. HOPEFULLY he didn't change the carbs to the 90-93 as I think they were bigger and of course most people associate bigger with better/faster. Maybe he just switched the main jet and richened the mixture with the added holes in the box and thought it would give more top end...

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I'm hunting around on the forums and the information is confusing.

 

How many mixture screws are there? 1 for each carb which is adjusting the pilot setting? Or is there a pilot mixture and idle mixture?

 I have seen people mention the idle mixture and pilot mixture so now I'm confused. I'm assuming they are the same and each carb has 1 screw for the pilot mixture but I am just confirming. Does anyone have a pic of the where the pilot mixture screws are? It would really help.

 

Just to clarify, the pilot mixture is affected by the slow jet size? So if he changed the main jet but not the slow jet, I can dial them to 1 3/8ths out and it should idle and start like stock? (assuming all else is fine) I've seen people on here say to run 2 turns out which is a full 5/8th more than what is listed in the pic above. 

 

 

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If someone to clarify this for me that would be helpful. 

 

As I understand there should be:

 

4 pilot screws

idle mixture screw

idle speed screw 

start up enrichment screw

 

Is this right?

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4 idle mix(1 on ea. Carb). 1 idlespeed( on throttle cable/ linkage)

that’s it except for screws on links to adjust throttle (plate) synch/opening

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Alright. According to the manual, being in Canada, I shouldn't have the D head screws either but a regular phillips head. I hope that is right.

 

Is there not supposed to be a startup enrichment screw? I saw it mentioned in the manual. 

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I'm going to make a separate thread abut the mixture screws.

 

 

Ok so I used some Ultra black RCV to seal the holes in the intake lid. Tomorrow I will confirm what carbs are on it and I will try to reset the pilot screws. Which way for rich/lean?

 

I don't think I will attempt taking the carbs off this time. I'm not in a position to the start the bike so all the lines and bowls are still full and I don't want to spill gas everywhere. If the rich problem isn't solved with the pilot screws then I will attempt removing the carbs in the spring.

 

 

 

 

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Ok so my carbs are indeed VP35As so that is good.

 

I went looking for the pilot screws and couldn't find them. I expected them to be easily accessed since I've seen people mention thumb screw upgrades and I couldn't see any screw that would be accessible by thumb screw if that makes sense.

 

I took a few pics, maybe someone can point it/them out? Maybe in the second pic it is that large gap phillips?

 

 

20180304_140416.jpg

20180304_140511.jpg

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All good, I know where the pilot screws are now. 

I'm going to remove carbs here next month and clean them and check the jets. I will report on that when I find out.

 

Next on my list is brakes.

 

 

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I sealed them up because they shouldn't be there. I removed the snorkel for sound. It's running rich as the original owner more than likely messed around with the pilot screw mixture and changed the jets. 

 

If they have been changed I will swap back to a #40 pilot which is stock and a #128 main which is just a tad richer than stock. 1 5/8 turns is the stock pilot screw setting,  2 1/2 turns like you said seems really rich no?

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19 hours ago, NateV8 said:

 

19 hours ago, NateV8 said:

 

. 1 5/8 turns is the stock pilot screw setting,  2 1/2 turns like you said seems really rich no?

 

Depends upon various factors.  The bike is too lean from the factory, so factory settings may not apply.

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  • 3 weeks later...
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https://www.bike-parts-honda.com/pieces-honda-detail-4754-13MT4L41-VFR750FV-1997-F__3201-VFR+750.html

 

 

Or go overboard:

https://www.pro-bolt.com/vaf/product/list/?Manufacturer=8&Model=189&Type=1&Year=9&category=%3F&prodtype=517

Funny that they list bolts with well nuts for the windscreen; I don't recall seeing those ever on my redslut.... :goofy:

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Hmmm it's the 6x14 fairing studs that I need. 

 

So I put my bike back together tonight. Here's a funny question... How do those gas tank cushions go on? Couldn't find a clear picture anywhere and I didn't see them when I took the tank off until they fell off lol. They looked self explanatory but just in case.........

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  • 1 month later...

The carbs are being taken apart tomorrow and cleaned. If the jets have been changed I'll change them accordingly.  

 

Slow jet should be a #40 and if it has been changed I'll change it back to #40.

 

Mains should be #125. If they are #130 or even if they are stock #125, should I throw in #128s? Everyone says they are lean from the factory, #130 seems a bit too high, #128 seems to be the best choice.

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Ok so the Jets were stock. #40 pilot and #125 main. The mixtures screws were 2 turns out. I'm going to set the mixture screws at 1 3/4 as suggested by my mechanic. The carb is dirty so maybe a good cleaning will fix my cold start issue. 

 

Should I bump to #128?

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  • 3 weeks later...

Well I got my bike back.  It definitely starts up easier with the carbs cleaned and synced. The only problem now is there is a bit of lean popping when letting off the throttle which I never noticed before. Does lean popping hurt anything?

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On 5/22/2018 at 10:12 PM, NateV8 said:

The only problem now is there is a bit of lean popping when letting off the throttle which I never noticed before. Does lean popping hurt anything?

 

if you want to fix that problem you could try opening the mixture screws 1/4 to 1/2 turn.

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Yea I guess It is decel pop and it isn't that bad. I only really notice it when I'm heavy on the throttle and then let off to idle. I read up on how it works and I'm not worried about it.

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