Camshaft advice

[ranton_rambler]

Matt, I improvised a bit as my garage is not as well equipped as some. Side cover off so that I can get a spanner on to turn the motor easily. Degree disc screwed into the end of the crank. Wire pointer so that I can read the position against the disc. Digital calliper to measure the valve movement from a reference point in the head. It’s a bit laborious but works well enough.
I think a dial gauge (DTI) would be the proper tool and it could perhaps be done with a head on the bench.
In addition to Nigel’s advice above,
we had a chat on the phone the other day. He’s pointed out that my new cam is not timed correctly, although all the dots are lined up. Having now overlaid my numbers on Jim Pianetta’s plots I think 1 tooth round on top bevel will be fairly close...
Ian

[ranton_rambler]

Cam has been retimed and I think is right now. It runs but I am really struggling to get a good carb setup for it.
It starts ok from cold, and easily when warm.
Idle is poor. I have to set it a bit higher than before, but could live with that. Also responds well to throttle inputs.
I’ve followed the same routine as previously and worked on the needle selection, settling on a D29 which is the same as it had with the old camshaft, but dropped by one notch. That feels good up to 3/4 throttle so I started trying some main jets today, working down from largest I have, which is 128. Smaller made it better, until it started getting worse again at 110. So I went back to 114 which seemed fine on the outward leg of my test route, but terrible on the way back. It did improve a bit if I coaxed it up to higher revs, but wouldn’t take full throttle below about 5000rpm.
Do these bikes suffer from cold air? It was only about 3C today.
Ian

[themoudie]

Aye Ian,

Cool/cold moist air is more dense than warm/hot dry air and whilst it might be a marginal difference, I would expect a slight weakness in the emulsified mixture to be more apparent on a day with temperatures ~3°C. The volume of air being drawn in through the venturi, especially for a threequarter to full throttle opening could be too much if the jet size is marginaly weak.

Because of the ambient low temperature, you might also have had some icing starting in the venturi on your return trip.

I'm having enough hiccups with my Amal and have been relatively 'lucky' with Dellorto carbs on the Morini motors, so apart from suggesting a next size larger main jet or raising the needle by one notch and the next size larger main jet, I shall say nothing more specific. If others think my comments are 'cobblers'; please say so, I am happy to learn.

Eldert or Nigel?

Good health, Bill

[Duccout]

I would agree with you Bill, I've always found cold weather always exacerbates any weakness in the carburettion.

[ranton_rambler]

I wondered about icing, but have never experienced it and it doesn’t seem long enough to allow it to develop. But reading a bit online, it’s a distinct possibility.
I have some other stuff to do, so I’ll perhaps leave this alone until weather improves a bit.
Ian

[ranton_rambler]

Dragged it out of the corner as both Guzzis are now sorted and the weather is a bit more suitable.
It started second kick after having stood since mid January and after a little warming up it was behaving as before. Brainwave - try a bigger idle jet. That seems to work as I now have a stable idle although mixture screw is almost fully in, so I may need to buy a 45. It’s got a 50 now.
So a trip up the lane was next. Seemed alright at first, just a bit of surging at about 1/2 throttle but as I went along it started to misfire really badly and was barely rideable. I suspect I’m having a repeat performance of a dodgy condenser so will refit the original in the week.
Ian

[ranton_rambler]

I'm almost ready to give up on this sporty camshaft now.

To solve last week's problem I swapped the condenser back to the old one and took it for a little ride of 3-4 miles and the terrible misfiring has gone.
But the poor idle is back. Today I have taken the carb off the inlet adaptor and cleaned it all up, checked for flatness and re-assembled it all just to make sure there is no air leak.
It starts pretty well and seems to respond to the throttle OK, but I can't seem to find a stable idle having tried 35. 40 and 50 idle jets.
With the smaller idle jets it will tend to sit at a fairly fast idle (2500+ rpm), but will usually just stop dead after a while. With the biggest I have (50) it seems better but needs the mixture screw fairly well in.

Does anyone know how much jet size range is covered by the range of screw adjustment? I am tempted to get a 45 but maybe have already covered that with my 40 + screw fully out, or 50 + screw fully in.

Iam

[themoudie]

Aye Ian/Iam,

I had similar problems with the 450 MKIII fitted with a cam of longer duration and lift than the OME. Nothing wrong with any of the individual parts, but the result of combining them was disasterous. Read the "450 Desmo carb" thread from page 3 to date!

"450 Desmo carb"_page3

As a result, increased wear of the exhaust valve and guide, due to fuel wash and now awaiting a new valve and visit to the machine shop!

Go canny and good health, Bill

[ranton_rambler]

I wouldn't say mine has been disastrous, but not delivering what I intended.

Anyway - a bit of progress at the weekend.
Another selection of idle jets obtained and we seem to have settled on a 42 for a reasonable idle. It seems much more sensitive than before and also seems to take a while to return to idle. I feel sure that must be telling me something but not sure what.
Road test up the lane showed a bit of hesitation at mid-throttle so I raised the needle one notch and that went away.
Onto the top road with some main jets in my pocket....slightly smaller than previous seems better but it started snowing so I packed up. As with the idle jet, it seems much more sensitive to small changes than before.
Perhaps will use it for a VMCC run next weekend and see how it rides in a range of conditions, with some jets in my pocket!

Ian