Jetting and valve set up

[Morizzi]

I'm just wondering what others have found to work in their 500.

I'm still not 100% on mine but I've just had the rear head work done and it is running much better. It came far too rich with the below settings:

PHBH 26
Main F135 R 130
Idle 45
Atomiser 262T
Needle X1-4 and very worn
Starting 55 but who really cares?
Slide 40
Float and set OEM.

I've now changed the following:
Main F130 R 127
Idle 40
Needle X1-3 new.
Slide 45

I'm thinking of trying a 50 slide then maybe bumping the idle jet to 42 but I'm very close to happy.

The exhaust valve was toast. Very poor seal and the guide was shot so got it K-lined. I'm thinking the valve gaps are just way too small for a push rod motor. 0.1mm for both? I don't think so. While the valve is setting in I've got the gaps as 0.15 inlet and 0.20 exhaust, the same as a small block Guzzi. I may settle for 0.1mm inlet and 0.15 exhaust but probably not. Even my Laverda 500 with DOHC has bigger recommended gaps than the Morini.

Just my findings so far. There are about a half dozen Morinis, 350's or 500's within 100kms of me but mine is the only one I know of, together and running. I recently got asked if I was going to do mine up. I simply replied it is together and running, it is done up.

I've run NGK BP6ES and Champion N9YC in it but now run the ND equivilant. It seems to be burning cleaner.

This is more for a FYI, get a bit of constructive feedback and hopefully get a few posts flowing.

Cheers

Rod

[MickeyMoto]

Hi,

0.1mm is what they always have been and always will be. No problems reported in 35 years!

I did once set mine at 1mm as I read the wrong bit in the manual that said for valve timing... bit clattery...

My carbs have 120 Mains, it runs ok, but seems to run out of steam at higher speeds in higher gears. I think the satndard size is 125(?). Why are the jets different back to front? Is it because the rear cylinder may run hotter because it is hidden behind the front?

Be interesting to hear if anybody else has done this.

Mike.

[Morizzi]

Hi Mike,

In every other bike I have dealt with the valve gap for exhaust is always a bit more than for the inlet due to the extra heat it endures. The inlet doesn't get hot exhaust gasses flowing past the base of the stem. I'm commenting as that the exhaust valve didn't come close to sealing, the guide was shot and it is a smaller, lighter valve. I'll be making sure it is at least 0.15mm in future. as that makes more sense to me. Personal choice. A wider valve gap will do no harm.

I don't know why the front main jet is bigger than the rear. (one reason for my queries) A lot of old Ducati bevel guys do the opposite and run slightly bigger jets in the rear to compensate for the perceived warmer environment. I've just dropped both jets down in stages from what I started with and this is where I have got to. Both plugs look about the same, I've used an IR thermometer on both pots and they are about the same too.

A guy who lives near me wrecked his front piston when he was riding WFO. One would think it would be the rear that would go first, all else being equal but this wasn't the case. My bike has been damaged in the front piston previously, before my ownership and I have a heat affected piston in the box of spares to show. Again the front.

Who knows the air flow around a motor? Who can tell if one piston gets better oil feed than the other? That's why I'm posting to try and get a bit of a feel for other's experiences. There are 5 or 6 Morinis within a 100km radius of me but mine is the only one that is running. All the others are in boxes or sitting dormant in a shed. Another, recently purchased, is about to meet the same fate as the new owner seeks perfection.

If the front is the most common then the larger jet there makes a bit of sense. The plug chop is really too close to call and the jets aren't that far apart really.

Anyway I'd like to know other's jetting preferences and if they have had a piston failure which one it was.

All for a better understanding.

Cheers

Rod

[EVguru]

Theory has it that the rear cylinder runs a bit cooler because it gets more oil fling from the crank.

In any case, Morinis have always listed identical jetting front and rear and I don't know of anyone who's had to run anything different unless using pod filters which often cause insoluable running problems.

I've worked with engines that were correctly set to ZERO clearance (pushrod just turns freely) when cold. The valves are steel and short so don't expand much, whilst the pushrods and barrels/heads are aluminium and can expand quite a lot. Depending on the rocker ratio and running temperature of the various parts, the clearances can increase or decrease with temperature. Have you ever checked what the clearance is when your engine is hot? Most Morinis are running more than 0.1mm clearance because wear of the rocker makes it impossible to measure with a feeler gauge. You can get feeler wires, but they're easy to damage. I reface the rocker tip so I can get an accurate reading. The design of the quieting ramps on cams has quite an effect on correct clearances. Closing up the clearances is quite a common tuning trick for race bikes where the regular maintainance should catch things getting too tight.

A worn valve guide is a good way to burn a seat out. Modern race practice is a guide material like Colsibro or Trojan and a clearance so tight that a lightly oiled valve will just fall under its own weight. The guide will have been brush honed to size rather than reamed, so you have an oil retaining finish.

Sometimes you'll find a cracked inlet manifold that seems to work just fine, but perhaps is leaning out the mixture when it resonates at the right rpm. Always make sure the carb intake rubber is doing its job of helping support the carb, the inlet manifolds had a hard enough job before modern fuels that are affecting many fuel system components.

[corsaro chris]

In the early days of the air-cooled Morini there was a lot of chatter about the rear cylinder needing different treatment to the front due to the thinking that it ran hotter. But if you look you'll see that by using the same head front and rear the exhausts are on different sides of the motor. Then, as Paul notes, others reasoned that the rear cylinder picks up a bit more oil than the front. Still others noted that the crows feet actually encourage oil flow (by condensation) on to and into the rocker / valve areas. So the whole thing is designed to work... and as the Founder remarked, designed to work at quite high revs!

Good riding (once the snow has cleared)

CC

[swtuggle]

It may be tangerines to oranges, but here's the recipe I've come to be very pleased with on my recently-acquired 501 Excalibur, at least until the weather warms considerably more:

PHBH28BS
50 starters
47 pilots
115 mains
40 slides
X22 needles set at middle of five grooves (from the original 30ESs)
264T atomizers
Unrestricted airbox (thanks to EVGuru)
Emgo 26" reverse-cone baffled silencers

Recently went from 50 slides to the 40s and just today, I went from X1-3 to X22-3 needles. Both helped to cure an annoying 1/8th to 1/4th throttle leanness. Riding to work at lunchtime found it to be running quite well. There may still be the slightest bit of leanness just off the idle stops while cruising. Have to get more saddle time to know for sure, and also to check the plugs.

Throughout all this carb tweaking, I haven't done specific throttle-position plug chops, but both fairly new BP6ES plugs have been showing a light beige on the ground strap with a still white insulator.

As for valve clearance, I'm keeping with the factory .1mm.

[Morizzi]

Thanks swtuggle. Interesting.

My bike wouldn't idle for long with an idle jet and slide like yours. It would foul up and just not want to play. The 28's instead of the 26's would allow for some of that though. 115 mains! Interesting too. X22 needle, I had to look it up as I'm not familiar with it. Very close to the X1's I have but mine only have 4 grooves. Your taper is just a tad longer. The 264T is a step richer. The 28's again would compensate.

I've left it for a few days hoping a few of you with the old 500 would chime in with your settings. Even if you just run EU or US standard it would be nice to know who has what and their impressions.

I'm still running the valves wide until the gaskets and seats settle.

One thing I have discovered is that my 15 litre tank holds 12.5. I fortunately didn't have to push it too far.

Rod

[swtuggle]

Rod,

Apologies to all for polluting the 500 page with 501 Excalibur info, but there's not much participation on the customs page, and this helps keep the thread alive.

As I mentioned about the cold weather contributing to my current jetting, I also think the short close-ratio 6 speed and final drive have a big effect on possibly masking any jetting discrepancies my bike isn't revealing. How so? As is, it revs through each gear like a trials bike, and each upshift barely drops the revs. I plugged the ratios of the 500 and 501 into a rpm/speed excel calculator, and the differences are striking. For example, your second gear is the same as my third, and yet my final drive is 3.21 to your 3.14.

I've ordered a 39 tooth rear to replace my stock 45 tooth to help space out my shifts and drop the top gear 60 mph/100kph revs from 5000 to 4300. Even then, with a .95 sixth gear, it'll still be 300 rpm higher than your .79 fifth 500.

This big ratio difference got me wondering, do you have to feather or slip the 500's clutch much during launch from a standstill?

Regards,
Steve

[swtuggle]

Rereading my own post made me realize I was shanghai-ing a carb discussion into a gearbox one. Sorry.

Back to the carbs, I'm wondering based upon your bike's settings and your feedback to mine, if I should bump my mains up to 118s (the largest I have on hand). I did notice a difference going from 112s to 115s, she pulls a bit harder and revs quicker with the 115s. But of course, without doing a plug check while holding it full-throttle, I don't know if I'd be too rich. I should have my son follow me on the highway and see if it smokes black, or any color for that matter. Only problem with holding it wide open is, with such short gearing, it reaches highly illegal speeds pretty quickly. That statement almost sounds like a complaint...

[Morizzi]

No problems Steve. I'm happy to talk 500's any time or place. Its not as though we are interupting anybody else.

My 500 Seiv has the 6 speed box too. I have a 40 tooth rear.

I certainly wouldn't want to try and pull up a steep hill, fully loaded with a pillion but it is OK for what it is. I don't know what the rear wheel rolling radius of an Excalibur is but if it is less than the 500 with a 110/90/18 on the rear then you should be OK. The 501 should be better than my 500.

Can't complain really. The little thing is a joy. I'm very lucky that I have a Lav Alpino and a Guzzi Monza as direct comparisons.

All the jets and settings are linked. There are places at throttle openings that each is more influential due to proportional fuel flow but there are no stop valves in there to cut off any circuit.

At WOT try the choke just a tad. If the bike improves then the main is small. Then turn the fuel taps off for a short time. As the fuel lowers in the bowl if the bike improves then it may be too big. You could try your 118 or simply raise and lower the needle. The 264T is bigger, much bigger than my 262T. The amount of fuel it can allow past an X1/X22 needle is something like 15% more at bottom of slide travel.

Doing the above test at WOT isn't really all that useful though. If you don't ride there then don't jet there, is my motto. If you find that the bike seems happier with the 118 but tends to foul at lower openings then I'd be looking at either a 45 or 50 slide or try dropping your idle jet. Dropping the needle a notch is an option too. One indicator that the bike is within a workable range at lower openings is if at best idle the mixture screw is around that 1 1/2 turns out. All the seals, etc need to be in good order, etc. When warm, from idle, slowly twist the throttle and see if the revs increase smoothly. If it hesitates then my guess is that it is too rich. You often read that owners increase the idle jet to remove this dead spot but in my experience it is usually too rich. Either way it can be adjusted out. Hold the throttle at the dead spot and with one of your other hands screw the mixture screws in and out to see if it improves. Othert than that hold the throttle in the dead spot for a while, kill the engine and have a look at the plugs. I have one of those colortune kits for this and as I've written, it is usually too rich.


When I buy an older pre owned machine that has been "adjusted" I invariably find that the happy spot is much closer to the OEM settings than the PO settings. The end of the carby era is slightly different as they leaned out the mixtures to meet increasingly tougher emission standards but still the happy spot isn't normally too far away.

Another trick is to clean and polish the end of the exhaust. Clean after every trip and see if there is any carbon. Plug chops as you have already mentioned a re useful too. Harder to do without burning your fingers on a Morini though. The guzzi is just a joy for this sort of thing.

Just some opf the stuff I do.

Hope it helps.

Rod

[milburn2990]

When I bought my 500 the carburation was rubbish. I have tried lots of things and the following is where I am currently.
Idle jet 45
Needle X1
Atomiser 262T
Starter jet 48
Float level 21
Main jet 125
Slide 40
The needle is 1 notch off the highest setting, although I suspect that this may be a notch too high.
I tried a 50 slide but the hesitation got worse and would be tempted to try a 35 slide if they were cheaper.
I have tried an idle jet of 47 and 50 but it had no effect on the hesitation.

This works well on a warm day although there is the slight hesitation at low throttle openings when the weather is cold. Its not perfect but its close enough to ignore the foibles.