Jet sizing recomendations?

[Guest]

[gentlemanjim]

I installed K&N air filters and a free flowing Supertrapp exhaust on my V50III.  I know I need to re-jet the carbs.  Stockk is 118 main and 45 pilot.  I'm thinking 132 main and 50 pilot.  Does anyone have any experience and recomendations in this area.  I know it balck art, but hoping I can get close to a smooth running engine.  Right now it goes flat and sputters at anything above 2500-2800 rpm under load.  In neutral it revs quite freely, but still falters wehn I attempt to rev beyond that point.

[Wayne Orwig]

No experience there, but have you tried just raising the needle?
And I would think that pilot change (45 to 50) is a bit excessive.

[guzzisteve]

You want to tune by throttle opening not rpm, 1/8, 1/4, 1/2, 3/4, full for main. Go w/euro spec then modify. If you want it to really run good, slides & needle & needle jet also. Start w/short tip mixture screws.

I got numbers and can PM you.  

[gentlemanjim]

Thanks I PM'd do you hae the parts too?

[guzzisteve]

I used to, but, not now.  Haven't  needed them.

[motoguzzibill]

I haven't played specifically with a V50 and am not sure what size carbs you have. What I can share is that anytime I have opened up the "breathing" on a bike, intake or exhaust, it ends up running rich. Now when you think about it you would guess by getting more air it would lean out, but not in practice.

If you have run it a bit is there any black soot around the muffler ends? If so you're rich. Look at the plugs are they sooty black? Not a great way to read mixtures anymore because of plug and fuel changes, but worth looking.

Try raising (richer)the needle a notch, and see if it gets and better. Drop it a notch (leaner) and see if it improves. At least you'll know which direction to go with the new jets. By the end of this process you will have a very nice collection of barely used dellorto jets. I've a great collection of Mikuni brass after adapting some flat side carbs to an SP1000.
Bill N.  

[gentlemanjim]

Exhaust is clean and plugs light frey.  Physics - more air with the same amount of fuel will alwasy create a lean condition.  I will raise the needle as well as larger jets.  I was hoping someone had a similar experince and could provide a base line for jetting my PHBH 28mm carbs.

[boatdetective]

Jim- I have to follow your lead here- I'm going to add Uni pods on my V50III & feel like i will needs some jet tweeking also. Best of luck. make sure you report on your progress- I know that proper jetting for these beasts can be a challenge.

[Furbo]

GJ,

FWIW - I'd disable  the accel pumps for jetting. They can give a false rich reading... You wont notice their absence in steady running, but you may have to accelerate a bit slower than your used to.

Start with the mains - I'd say 125 might be as large as you'd want to go, but up to you. Just have a collection of sizes before you start.  do your plug chops until your happy - then work down.

One up on the needle should get what you want - unless you're going to experiement with different needle tapers & needle jets.

I'd doubt you'd really need to change the pilot, but if so, one size up would prolly do. The screw gives a good bit of adjustment to that circuit.

Once it's done, re-enable the accel pumps and adjust as needed (many are pretty rich, as it's a crutch on lean jetted engines for what the midrange jetting should be..).

Then - balance the carbs. Preferably with carb stix - but if not, there are other cruder but effective methods.

corragio e buona fortuna.

[Morizzi]

Exhaust is clean and plugs light frey.  Physics - more air with the same amount of fuel will alwasy create a lean condition.  I will raise the needle as well as larger jets.  I was hoping someone had a similar experince and could provide a base line for jetting my PHBH 28mm carbs.

Physics: The faster the air flow through the carb's venturi the more fuel it can suck up through the jets, if everything else is equal.  I'm not saying that it will be richer but it won't be as lean as you expect.  It won't be the same amount of fuel at all.

Jim, please? For anyone to give you any type of decent advice it would help if you provided all the relevant information. 

Do you still have the standard 50 slides and X6 needles on the 3rd notch? Have you checked the float heights and are they still the 11gr floats?

What heat plugs are you running? A V50 is recommended to have Bosch W5DC or equivalent. That's NGK BP8ES. If you are running anything hotter then you should try and take that into account when trying to read the plugs.

I usually find that most owners with limited carby experience tend to go too rich. Why are you changing the jetting? If the exhaust is clean and the plugs are light grey what are you chasing? The manual states that a V50 should use about 4L/100km. If you are using anything close to that sort of fuel rate on the open road  with limited stops then you will be doing well.

If it starts well, idles easily, doesn't foul the plugs, accelerates from stop evenly and runs nicely at wider throttle openings and gives a reasonable range then I'd leave it like it is.

A previous post has highlighted that it is throttle openings that need to be assessed against results, not revs.

None of my PHBH carbs have pumpers. The U.S. may be different, I know the VHB's were different there but I don't know about the PHBH's.

Good luck with it but if it ain't broke, don't fix it. 

[MotoMatt]

My wife had a V50III for awhile that had the K&N pods on it but stock exhaust. The previous owner had raised the needle I think but it was still lean when cruising at higher speeds as it would surge a little. I went to a 130 main jet and it was perfect and ran great everywhere. I think it had the stock pilots but I'm not sure. and I don't remember what setting the needle was on. By the way I'm around 700ft elevation. Hope this helps.

[gentlemanjim]

Thanks for all the input.

To recap and respond to your questions:
1. I believe everything in the carbs is sstock USA
2. I'm running the Bosch that were recommended on my Dyna S post as I thought that was the issue equivilent to BP7ES.  Maybe should be cooler as it runs good warm and backfires and falaters when fully warm under load.
3.Regardless of the plugs appearance I ride for more than 1 mile and lose power and it skips and sputters and won't accelerate.
4. If increase the throttle opening slightly holding dwon to 25oo rpm it is fairly smooth, but stilll sputtering and interminently accesrates in nano seconds and goes back to poor response.
5. I don't recall accelerating pumps when I cleaned them
6. Oh yea it's broke.
7. I'm going to tear them down this weekend and re-jet, new float needle, raise the needle and a thorough recleaning
8. Now I'm ready for some good luck

Thanks agian

If I'm going off the deep end let me know - please

[Guzzistaracing]

Physics: The faster the air flow through the carb's venturi the more fuel it can suck up through the jets, if everything else is equal.  I'm not saying that it will be richer but it won't be as lean as you expect.  It won't be the same amount of fuel at all.
[/quote]

Yes, but the jets limits the amount of fuel that can be suct into the airflow! That is why you have to change the settings. This is the whole point of the different jets!

[Two Checks]

More air doesn't increase the speed at which the air goes through the carb, only the amount. Improving the breathing LEANS the mixture.
If you put a bigger carb on with the same size jets it would be leaner than before.
More air, but it flows at the same rate. The air cannot flow any faster than the piston can draw it into the engine. Improving exhaust scavenges the cylinders even more, creating a further lean condition.
The only way to increase the rate at which the air enters the engine is to increase engine speed.

Even if the air went in faster and picked up more fuel it is still lean. If the mixture is lean to begin with and more air is introduced, the added fuel just returns the mixture to where it started.

The carbs need bigger jets.
I have no suggestions on a V50 except to richer one step at a time until the plugs look right and it runs right.

[Diploman]

The V50III incorporated a number of useful updates/changes from the original V50 and V50II.  Unfortunately, a couple of the changes were steps backward, notably: the reversion to points ignition vice the Bosch electronic ignition on the earlier bikes: and the use of 28mm PHBH carbs instead of the 24MM VHB's used on the fist two series.  The Monza also used the same 28MM carbs.  These PHBH's have historically proven problematic.  In Guzziology (Ch 7-23), Dave Richardson has some unflattering comments about them:  "V50II and Monza.  These bikes are an exception to the rule that Moto Guzzi knows best how to make their bikes run right."......"I have tried various combinations to improve these bikes but have nothing worked out I would recommend.  I'm open to suggestions."

If, after experimentation with different jettings, you are unable to achieve smooth running, possible solutions might include:
--using 24mm VHB's from a V50 or V50II;
--using Mikuni roundslides (cheap, readily available, a plethora of jets easily obtained).

Good luck, Jim.  Hope you can get your gorgeous cafe project to run as well as she looks.
Will

[gentlemanjim]

Another thought!!  Because it runs fine while cool and only acts up whenhot - Could it be the plugs are too hot a heat range?  I recallmany moons ago on a Virago that it acted the same way until I put in colder plugs.  I have BP7E, I think it calls for BP8E.  which way does the heat ranges go higher numerically hotter or colder?

[Two Checks]

Acts up when hot-too lean. That's why it gets hot, too.
The plugs are grey, indicating too lean. They should be tan. Fatten the pilots. Once that is done, then tune WFO with the mains.

You have plugs one heat range colder than spec.

[steamdriven NZ]

When my Monza ran the 500 engine it had free flow pipes and pod filters, and was set up as follows:

120 main jet
50 idle circuit
60 start circuit (the tall sticky-out one)
Needle clip on the bottom groove (i.e raised to maximum)
Idle screw 1 1/2 turns out
Plugs are BP7ES

Fuel here is 96 unleaded, altitude sea level but would run quite happily 3-4000ft which most of our roads are below at a guess.

When the engine was rebuilt at 100k  I got Dave C to put some pod filters on it (it already had free flow pipes), and he set the bike up using an exhaust gas analyser that sat on the tank. He'd go for a ride and see what it would do, change things until it was right. It did a further 40,000km with these settings with no problems.

 

Hope this works for you, it did for me.
Kev.

[gentlemanjim]

SUCCESS!!
I rebuilt the carbs today.  132 main , 50  pilot jets, float needle and seat.  Left the needle alone as I think I may have over richened the main jet.  Starts quickly, little choke, crisp throttle response on the road revs right up to 7k, could have done more, but being carefull with an unproven bike.  Took it out for a spin of about 5 miles ran great no hesitation, crisp throttle and a steady idle.  Now I need to sync the carbs.  Which should be easy with a carb board, but I'm a bit confused about the throttle cable adjusters.  I backed them down so there is a little slack in the throttle grip to the point that I think Iitwas idling on the adjuster speed screws.  Just don't know if the slack is equal on both carbs.

Thanks to all those that contributed advice, support and recommendations.  If it would only warm up I'd take for a real ride.

Thanks,
Jim    

[boatdetective]

Jim-

Thanks- I'm following your lead as i am putting on pods myself. You said 50 pilots- is that the idle? what about the start jets?  Also what position were the clips on your needle?  THANKS!

[gentlemanjim]

132 main , 50  pilot jets, float needle and seat.  Left the needle alone in what ever poition is stock.

In the picture above the brass jet between the floats is the pilot.  The jet that screws into the bowl bolt is the main or high speed pictured to the right the main pictured to the right facing up.

[Murray]

SUCCESS!!.  Just don't know if the slack is equal on both carbs.

Thanks to all those that contributed advice, support and recommendations.  If it would only warm up I'd take for a real ride.

Thanks,
Jim    

When you balance the carbs you'll be able to dial out any difference in the cable buy seeing if both carbs pick up together or one leeds the other. Just remember its the carb with the lowest reading that is working harder, which I managed to suff up when I did mine the first time.