lining up the dots – timing, cams, jetting

[Commodore]

All, Thanks much for all your help over the years.

I'm having running issues that are similar to those discussed in these threads. I thought I'd start anew and address each one separately, starting with timing and dot alignment.

viewtopic.php?f=3&t=3002&start=150
viewtopic.php?f=3&t=3344
viewtopic.php?f=3&t=3353

I'm nearing completion on my '66 Monza bitsa with a Mach1 spec engine that George Vincensi prepared, with a green/white cam, and high comp piston. I did a complete Electrex 12-volt conversion with electronic ignition (STK-161), and new Amal Concentric 930 carb with choke. Compression is 130-140 psi cold (on 4 kicks).

I have about 35 miles on this setup, and following problems have gotten worse: Hard starting (20 kicks); Bad running (missing – seems like it can't rev any higher) at ¾ throttle and above and most recently, good idle and revs until just conking out after a mile... Please note that not having had a running Duc single before, I do not know what to expect with the green/white cam (although I was cautioned that this motor would require hi revs).

Replaced timing gear shaft seal after a leak started, and feared that I mispositioned the gear when it came out with the timing case cover. So I'll start there...is my timing correct?

The following picture show my timing dot alignment: a) when the ignition gear and crankshaft gear dots align with dots on oil pump driving gear, bevel drive dots are not aligned. b) bevel drive top and bottom gear dots align.

Next to discuss: plug experiments: NKG B8HS and B9HV; carb experiments: 210 to 250 main jets; needle in all three positions; 106 pilot jet ; slight changes in timing adjusting the pulser unit - without solving my problems.

Thanks!

Timing_OilDotAlign_BevelNot.jpg

BevelLowerAlignNotTiming.jpg

[Duccout]

Hi,

It looks like your timing is out. The bevel gear dots should line up at the top and bottom when timed correctly, then the crankshaft dot should be timed to the oil pump gear and the ignition gear.

Colin

[Geordie]

As Duccout has explained plus the timing is 'hunting tooth' therefore out of alignment for several revolutions until aligned again. I don't recollect the number of revolutions but you might try a few before starting over.

[Geordie]

Put "hunting tooth" into search on this site on the main discussions page. There are several posts. I have not checked your links above.

[themoudie]

Aye Commodore,

I agree with Colin, it would appear that your valve timing is incorrect. However, the "hunting tooth" design of the bevel gears maybe giving us this impression.

Firstly, before you do anything else, may I suggest that you clean the oil from the timing marks on both sets of bevel gears, the end of the crankshaft, the ignition rotor (points) drive and the oil pump drive gear. Then apply a quick drying white typing error correction fluid, such as 'Tipp-Ex' to all of your timing marks, it makes them much easier to see and being in the timing mark 'dot' it doesn't wear/rub off and yet wont damage the engine if it becomes dislodged.

Ensure that the cam bevel gear and it's partner at the top of the vertical drive marks (dots) are aligned as are the lower bevel pair's marks (dots). With the piston at TDC. Then insert the oil pump drive/idler gear into it's bush, ensuring that the left-hand timing mark (dot) aligns with the sometimes obscure mark (dot) on the crankshaft gear. Then you should be able to insert the ignition timing gear into it's bush and align it's mark (dot) with the right-hand mark (dot) of the oil pump drive/idler gear.

My reason for bracketing (dot) is that the 450 engine, with which I am more familiar, uses a scribed line as the ignition timing mark rather than a dot that is used on all the 250 and 350 engines.

The Haynes Ducati workshop manual has four images (pages 54-55, images 42.1-4.3b) that show these arrangements and if you do not have access to a copy then I shall try to oblige with a scan of the images and accompanying text for you.

I hope this helps.

Good health, Bill

[Eldert]

timing is OK . if you move the oilpump gear 2 teeth clockwise everything lines up .

Eldert

[Duccout]

Well spotted Eldert! It's obvious now I've looked again.

Another bike with 'carburettor problems' - join the club!

[themoudie]

I apologise Commander, if indeed both the valve timing and ignition timing are correct.

But, I would still advise the use of some 'Tipp-Ex' and a check due to the 'hunting tooth' design.

If indeed, you have carburation problems, you have my sympathies. My 20 month quest caused some angst, but after negotiating some unexpected hurdles and some of my own making. I now have an AMAL MKII 2932 working well on a '74 MKIII 450. BUT, each engine/carb/exhaust system combination is unique and any jetting suggestions are only possible starting points. A run on a dynamometer, could have identified my carb problems, but I chose not to use one. Luckily, for me, I have rural roads that are relatively quiet, on which to make my test runs. In an urban environment, testing would have been a different matter and the dynamometer more of a necessity.

Good health, Bill

[Commodore]

Problem one identified! I'll be getting things back together this afternoon, and let you know how the performance is. And relaying one story of my experiments: I was amazed at how a slight adjustment to the timing (at the pulser ring) affected kickstarting - from no kickback to a noticeable kickback. Thanks for the "continuing education", which is why I took this on from the beginning!

[etsjw]

Greetings,
I have a 66 Mk3 equipped with a G&W cam , PowerDynamo ignition, standard compression piston and an Amal 930. The exhaust is a Vic Camp megaphone style muffler the was acquired many years ago. To say it is free flowing is a bit of understatement (but when riding if I'm not seen at least there is a chance I'll be heard).
For the carb, a 106 pilot is fine. I found a 3.5 slide is required and the needle should be in the middle position. I use a 230 main and this results in a slightly rich mixture at WOT. Check the fuel level in the bowl and adjust the float as required - I can't recall the exact height but this is covered in many on-line articles.
Here is the starting procedure I use that results in first kick starts 95% of the time:
1-If the bike has been sitting for any length of time, free the clutch.
2-Choke not required if ambient temperature is 60F or above.
3-Tickle carb until fuel runs out the weep hole.
4-Increase idle speed set screw 1/2 to 3/4 turn.
5- Open throttle 1/4 turn.
6-Give it a robust kick!
With my bike, an air screw opening of about 3/4 to 1 turn seems to work.
Regarding plugs a NGKB7HS is perfectly fine for road riding. A plug gap of .028" is OK.
Good luck!
John
















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