Different carbs for our 4th gens also new jet kit questions

Hey everyone,  have a questions about our 4th gen carbs as well as some questions about the simple jet kit I put in.
Was reading the Honda Repair manual and it listed for after 1993 models,  VP34A for 49 state carburetors,  VP33A for California and VP35A for Canada models.  I have a 1996 VFR (California).  Are there really any differences to these carbs... internally/externally?  I mean other then main jets/pilot jets and pilot screw settings... are there differences other then this?

On my '96,  I have the airbox mod (snorkel removed) a K&N airfilter, removed PAIR system (properly blocked off) and Delkevic slipon exhaust and recently put in a simple jet kit.  This jet kit had #130 rear main jets,  #135 front main jets and pilot jet #42.  Also had a extra shim for each needle.
Prior to this jet kit install,  the VFR was a bit hard to start every time when cold.  Even with very warm temps in the garage her in Arizona.  I would have to use the choke at least 50% open.  Even then was still a punk to start.
Did a full carb cleaning and replaced the jets as listed above, added shim and re-sync'd the carbs (very close now, 23hg #1, 21hg #2, 21hg#3 and 21hg #4) and replaced the pilot screw shim and o-rings.
Did not have a full rebuild kit though.

Went through the procedures of setting the pilot screw adjustments per the honda repair manual as best we could (did not have an actual 50rpm guage to go by).
Bike still, when cold is a pain to even start unless 50%-75% choke is used.  When hot,  it'll fire up after a couple minutes without a problem... but after an hour or so,  you can tell it's going back to be a punk to start sorta.  Also, at freeway speeds...  I notice when fully opened throttle up to redline,  there are a few noticeable flat spots that are felt in certain areas between 8500 to 11,5000.  Not huge ones,  just a couple spots of hesitation/stumble (?).  1/4 throttle to almost mid throttle points seem strong when rolling on it good.  I don't know if it's running really lean or not though,  but on decel (throttle closed) there's a few small pops as the bike nears idle when slowing down from blipped down shifts... but not really loud pops at all.
The Honda repair manual states 2-3/8 turns out for initial set on California carb/bike.  But 49 state states 1-5/8 turns out for initial set.  Should I try the 1-5/8 and go from there?  Or do the different carbs listed for the different bikes not allow the swap of pilot screw setting adjustments?

I was able to track down the owner before me,  who had put on the most miles and mentioned that valve adjustments were not checked or done.  My VFR has 21,960 miles on her.  Could this be an issue to the difficulty in cold start ups?  New fuel pump, new fuel pump relay, new fuel filter, ultra clean gas tank, new fuel hoses, new NGK plugs, no know vacuum leaks, new battery,  strong spark on all plugs.
Not super knowledgable in carbs or trouble shooting.  Any help or suggestions fellow viffer owners?  Any would be greatly appreciated!

Just quickly looked at the jets numbers, but those jets sound HUGE for that setup.

I concur with Yoshi. Even with the K&N and the slip on, I'd  at least drop those fronts down to 130s to match the back. Maybe drop those (the rears) down to 128s and then look at the plugs. Because of the cold start issue, are the little 'booster pumps' that richen the mixture on start up working? Good luck.

I don't think that jetting is too far off at all for a de-snorkeled bike with exhaust.. I would ditch the stagger, because thats something thats done more so on air cooled setups that actually have a significant diffrerence in temps between front and rear banks. I run #42 Pilots and Either #132 or #135 mains, been a long time since I jetted it, and I don't use kits. I'm leaning more towards them being #132's though.

As far as low speed adjustment, mine seems to be happiest in the 2.5-2.75 turns out range.

FYI. I'm going to run a modified airbox and different headers, and I'm only going #130 on the mains and only a tiny bit more on the pilots. Slow jets are still #40s. A de-snorkeling and a slip on shouldn't change the jetting at all. Maybe go up to #128 on the front and #125 on the back at most and stay with the stock pilot settings. My other stock 4th gen has what you mentioned and runs great on stock settings.

If you think a modded airbox and an exhaust don't require jetting, you shouldn't be handing out advice.. Just because you're jetting your bike lean, doesn't mean thats what everybody should do. And what are you talking about #40 slow jets but a tiny bit more on the pilots? The pilot jet IS the slow jet.

And FYI, I'm a trained carburetor specialist, my work is known all over the globe and has won people countless championship races.


PS: my bike has also layed waste to an 08 ZX6RR with 140# rider, and I weigh in at about 235. I don't give out advice unless I know exactly what I'm talking about.
Edited by NakedViffer, 05 May 2012 - 08:45 PM.

Well...the main jet is a number #125, and the slow jet is a #40, and the pilot screw should be turned 2.5 turns out. Those are the stock carb settings. The slow jet is just a bit different than the pilot screw.

And my bike is not running lean by any means, 100% sure of that. I may not be an amazing mechanic, but I'm not an idiot by any means. A slip-on and a de-snorkeling isn't going to change your rich/lean situation enough to do any serious adjustments. And according to their tuning sheets, Factory Pro has found the same thing to be true as to what I originally suggested (#128 mains max, stock slow jet, 2.5 on pilots).

 YoshiHNS, on 05 May 2012 - 09:10 PM, said:

Well...the main jet is a number #125, and the slow jet is a #40, and the pilot screw should be turned 2.5 turns out. Those are the stock carb settings. The slow jet is just a bit different than the pilot screw.

And my bike is not running lean by any means, 100% sure of that. I may not be an amazing mechanic, but I'm not an idiot by any means. A slip-on and a de-snorkeling isn't going to change your rich/lean situation enough to do any serious adjustments. And according to their tuning sheets, Factory Pro has found the same thing to be true as to what I originally suggested (#128 mains max, stock slow jet, 2.5 on pilots).


While the masses may call it a "pilot screw" thats not the correct terminology. The screw is your 'low speed adjustment', because it adjusts the feed to your low speed circuit.. Since you know 100% its not lean, what do your AFRs look like at cruising throttle? How about wide open?

You clearly stated you are "going to run" as in pre tense, so how are you so sure?

Factory Pro can say whatever they want, they aren't in the business of tuning VFR's, they are in the business of making money by selling horribly overpriced jet kits. Are you familiar with volumetric eficiency? If you understand VE, you would know that any changes that alter intake or exhaust flow effect it. I have been tuning engines for nearly 12 years, and that includes dyno tuning, and racetrack tuning. If you can't take me at my word that changing intake and exhaust requires jetting changes, you need to go study the internal combustion engine a little better. Or better yet, go to the dyno or drag strip with an assortment of jets and find out for yourself.

On the exhaust, I can somewhat agree, you can change that and get away with not jetting, but the intake is a different story, especially when coupled with a modified exhaust. I don't know about you, but I like my engines, regardless of what they may be in, to run as best as possible, and to make as much horsepower as possible. If you're OK with sub-par results, then don't change anything for your modifications.. Its your bike, but don't tell others to do the same thing unless you know for a fact they are NOT interested in having their engine running at 110%

I just don't think its fair to give advice to people based on a theory. You're obviously basing this information on your theories, and stuff you've read on the internet, I have real world experience, which usually trumps theory, and internet dis-information.
Edited by NakedViffer, 06 May 2012 - 12:07 AM.

Sorry for the terminology mix up there. It's what I've always called it, and it's how every motorcycle manufacturer identifies them in their manuals. So I guess they are to blame for the masses being confused.

Yes, the FP kits are overpriced. But part of the price is getting their own data and the data of other people as well as their exact setups, so you can see who has what working with which mods. Some of them have even been tuned on the dyno.

For my STOCK bike, I have not adjusted the jets. K&N filter and slip on. For the bike I'm working on, I have it set to only #130 based on what I've read other people to experience. Is it right? No idea. I'll find out when I finish it.


To the OP: To get it right, you started with stock jetting, and it wouldn't start easily. Then you jetted it, and it still wouldn't start easy, but then you had hesitation at high RPM. So can we assume that you didn't have any problems once the bike was warmed up on stock settings? If you replaced all that then I'd take a look at the fuel filter to make sure no debris got into it after you replaced it. Had that happen to me once before. I'd then suggest to go back to stock settings with the 'low speed adjustment' set to 2 1/2 - 2 5/8 turns out. If it improves a bit, go one bit richer on the mains. Worse case, you might just have to take it to a dyno to get it tuned right if you have that many problems.

OH, also make sure you have your airbox properly sealed and that your carb boots are on right and tightened down. I would put the snorkel back on, because I think it doesn't do anything to help the engine by removing it. But that is strictly my opinion, but you can do your own research on what people have found out about what the snorkel does or does not do.

What's the Altitude like in your area?

My 4th gen has a TB slip-on and with the stock airbok the A/F is dancing around the 13.1 ratio.

Is there someone/somewhere nearby you can get the A/F checked with a sniffer?

There are two tunners in the uk of v4s one called ron grant and the other tony scott i think ron is retired now they made rc30s go very fast anyway when they jetted the v4 hondas always they would run a slightly lager main jet in the rear carbs as always with the v4 the rears run hotter than the fronts.

Instead of diving in, I'm just going to dip my toes in the shallow end to add that, just like pants and shoes, jet sizing is not created equally.

You need to add specifics if you want specific results.

What am I missing here? Every bike with a choke I've owned needs full choke at cold startup (ummm, that's what it's there for) and you turn it down from there as the engine warms until its no longer needed.

Been riding since now for 36 years and this is always tge case unless it's jetted incorrectly. This 50% vs. 75% choke thing makes no sense at all at a cold start, no matter where you live.

OP can you describe what you mean by a "punk" to start? Does it spin and not catch? Catch and not stay running? Little more info may help.

And you cannot jet based on thought or what others have done and call it good, it's a science and every bike will be slightly different to run optimally. If you open up an intake and an exhaust you need to make adjustments; a slip on and K&N should be OK stick but will pop as its bordering on lean.

Mike

Someone fix my ignorance . . . If I was going to stagger my jetting, wouldn't I make the back cylinders richer than the front.  The backs would tend to run hotter, and a richer mixture would help keep them cooler.  And I agree, it seems that this would be much more effective with an air cooled.