Red glowing pipe - high idle only - mark 3 250

[Crazygreg]

Hi,

i'm having some issues on my 1965 mark3 250 narrowcase , the pipe is glowing red but when i "read" the spark pug it seems to be running rich (inside exhaust channel it's really dark too), idle works when the bike is warmed up, but die if i accelerate slowly so i need to keep the idle over 3000rpm (bad i know).
I initially thought it could be the slide cutout but tried 2 different ones and do not seems to change anything, the bike is also quite insanely loud.. (race megaphone with muffler pack and supertrapp inside)
here is the specs on the engine :
approx 50 miles on the engine since complete rebuild.
74.6mm high compression piston coated top and skirt (compression read 200lb/in2 loosely , which seems high compared to my other bikes)
40mm intake, 37mm exhaust
monza cam
SSI 29 with SS2 remote float, velocity stack, level just under the mix screw adjustment, 80 slide with needle on the 2 notch from the top, 122 main jet, idle 60.
Powerdynamo 12V electronic ignition.

need to re-check the timing but the bike bump start quite easily using the decompression lever from a 350.

any info greatly appreciated,

Greg

[graeme]

Sounds too far retarded

[Bevel bob]

It may be you are running retarded, Somewhere around 35 degrees advanced 5 to 8 degrees static is where mine is (depending on what ADV unit fitted). Also possible you are weak on the slide but rich on the needle jet, or weak with a bit of oiling up to confuse the plug reading. Mine runs a 60 slide and a smaller 260 needle jet and a110 main (though I doubt you are on the main long enough for it to show++++unless you are following me!!).I would have suspected a leaking Exhaust valve, but not with that compression , but it could stick when hot and not show on cold test.Also check your fuel flow to the carb, a blocked tank cap pin hole stopped me a few times.Jack up the float level till the carb leaks then back off just enough to stop it dripping.See what effect that has. Main jet can be soft soldered and sized with a sewing needle and a mike if no alternatives availiable. If you can get it to tick over then you are lucky or something is wrong!!.

[LaceyDucati]

Hi Greg,
Powerdynamo has switchable curves, is it switched correctly? Think you need to put a degree disc and a pointer up and get a strobe on it to see what’s happening first. Assuming that is OK, you say you have other bikes are they Ducati singles? If so a whole similar size carb swap will usually narrow down a major carb fault.

Super trap, Hmm, never got one of them to work that well, We found with a small amount of plates they ran quiet and didn't go. With a large amount of plates they went, but were noisy and when you removed all the plates and end, the bike still went and was similarly noisy! Exiting exhaust gas sideways also contravenes UK race and probably road regs, only my personal limited observations. Have you got enough plates in it, not to be to restrictive, I guess so if it is noisy.

Nigel

[Crazygreg]

Thanks a lot for your answers!
my other bikes are japanese, so no luck with the carbs (was thinking on trying a Keihin 29mm smoothbore CR but seems too large to fit)
...I have a VHB30 and a VHB 29 that i could drop on to try, didn't get the time yet, but tried the carb on my friend scrambler once and it was working properly, i'm planing on modifying the SSI main jet to accept modern dellorto's\mikunis, easy to find and cheap alternative. i would love to use the SSI as it is to my opinion... the best looking carb!
i was thinking that the bike might run retarded, dropped the powerdynamo when i didn't had my top end ready yet, using the lower bevel coupling indication that Tom give in his book.
i need to check that too, i sent an email to powerdynamo to ask them about the different curves option but didn't get any answer.
Will try your settings Bob, my main jet might be too large as well.
Did anyone ever tried to adapt a VHB accelerator pump on a SSI? wonder if it would help with the lower throttle response...

[double diamond]

The 60 idle jet seems rich, usually 45-50. What have you done with the high speed adjustment plunger (mistakenly refered to as “choke”)? M14 needle? 265 needle jet? You identify the cam as a ”Monza” cam. Is this a standard Ducati Monza 250 cam, which has quite mild timing? This would be a curious choice to run with a high compression piston/Mk3 head/SSI 29 carb. If so, would account 200 psi cranking pressure. An exhaust header that is glowing red can be an indication that the cam timing is advanced. Matt

[Bevel bob]

The bike should try to kick back if the timing is close,no kickback ? its likely to be retarded,how much advance does your system give?.Kickback seems to start at about 8/10 degrees static.

[Crazygreg]

I tried a 50 idle jet, it was worst, the "choke" brass plunger is in with the spring pushing on it. the needle is M14, 265 nebulizer.
I dropped a monza cam as I thought it would be wiser for engine break in, i have a unknown race cam with plugged oil channel that I could try.
All the dots are aligned on the bevels, so timing wise it should be good on the cam side at least, will re-check the ignition timing.
if started with the kick, the bike does kickback, i need to use the decompression lever to kick it, as well as bump start it.
Will try all of that as soon as i get a little more time

thanks again, will keep you informed if anything work!

[Crazygreg]

you guys were right, the engine is firing at TDC, and advance up to 28degree when rev up, for some reason the timing mark must be off on the flywheel, or I didn't set TDC properly (or slipped 10 degree when tightened the main gear
Still, with bad timing, got the bike to idle smoothly with a 29mm VHB.

[Crazygreg]

Bike is running like a champ now! using the VHB, and proper timing, as well as a racing cam with following lift:
9.85mm exhaust
8.55mm intake
will post pictures later, i have another cam with 10.5mm lift ex and 9.5 int too but seems overkill.
however,the bike seems to have a little play between the head and the top bevel bearing cup (the one that fit in the head on top of the column, is there oversize bearing cup?