CCT change and engine dies after 4-5 minutes

[kitsun]

Hi All

Changed my CCT with a pair of new auto CCTs that was sitting around on the shelf. Checked the valve clearances and only the front 2 exhausts valves and the left front intake valves need adjusting as they were all tight and below tolerance. Put everything back together, checked cam timings - on RT rear cam lobes were inward RI and RE marks outward and level with head. All good.

Rotate 450 degrees (1 and ¼ turns) to FT mark - cam lobes pointing outward and the FE and FI marks pointing outwards and level with head. Double check, rotate 270 degrees (¾ turn) to RT and recheck rear cams and lobes pointing up and inward and RE and RI marks level and pointing outwards. All good.

Rotated many time by hand and no valve and piston interference. Rotated with the starter motor (kill switch activated) to circulate oil round the system, Airbox and tank back on.

I fired her up and started first go and sweet idling sound and the clacking of the old auto CCT gone. But here's the bummer after about 4-5 minutes of idling, the engine started running rough and then stalled. 10 minutes later i started again and again fired up first go. i revved it up to 8000 rpm with no issues but about 15 seconds after that the engine started running rough and cut out again. It would start again after about 10 minutes and again fired up first go but with a big backfire this time which set the village dogs barking.

My first thoughts are that its a fuel starvation issue. Maybe i've got the pet rock set wrong? it rotates 2 ways, full clockwise and full anti clockwise. which direction is fully on? I've got it set as full anticlockwise. I tried setting it full clockwise and the engine dies as well.

[Wicky]

Vacuum hose connection....

[Stratman]

Is the vacuum pipe on the right place on the petcock?

[AMCQ46]

It's what they said. You didn't put vac pipe on the correct part of the tap.

It's the one on the back not the one on the bottom

[bazzashadow]

I had this problem once and I can`t remember what one,
but I had one of the fuel pipes (from tank to carbs)
over something, instead of under it(bad memory, can`t remember what it was)
took us ages to work out what it was
and it all started because I wanted to cut some inline filters in

[TheGingerBeardMan]

Top Tip for removing hoses and/or tubes from fuel tanks, ensuring correct replacement:

Take a bottle of Tippex correction fluid.

Spot each hose AND the "nozzle" it comes off from, as you take them off.

Remove one hose/tube at a time.

So, 1st hose (doesn't matter which one) is marked with one dot, and so is the connection.

2nd hose is "spotted" with 2 dots (and the connection)

3rd hose and connection has 3 dots...etc.

Then, when you come to connect it back up again, it's easy to see what goes where.

[MacV2]

Top Tip for removing hoses and/or tubes from fuel tanks, ensuring correct replacement:

Take a bottle of Tippex correction fluid.

Spot each hose AND the "nozzle" it comes off from, as you take them off.

Remove one hose/tube at a time.

So, 1st hose (doesn't matter which one) is marked with one dot, and so is the connection.

2nd hose is "spotted" with 2 dots (and the connection)

3rd hose and connection has 3 dots...etc.

Then, when you come to connect it back up again, it's easy to see what goes where.

Or take a pic of it before you take them off & refere back to it on reasembly...

TBH it's only the Vac hose that is an issue. The other 4 only go on one way...It's not rocket science...It's Storm Science!

[Cadbury64]

Yeah, what they all said!

The fuel tap is closed when rotated fully clockwise and open when rotated anticlockwise (when looking from the front of the bike towards the rear).

The vacuum petcock hose comes from a fitting on the left side of the rear carb intake, and plugs into the fitting on the back of the vacuum tap. The other hoses on the tap are two biggun's that go from either side of the tap to each carb, another biggun that is the drain from the fuel cap overflow and another small one that is the fuel tank breakethr, both of these last two are located on the underside of the fuel tank.

I've had a similar experience myself of starting the bike up after a service only to have it starve and die, because I forgot to open the fuel tap!

[Kurt999]

If it's not that, make sure you haven't pinched one of the carb vent hoses

[kitsun]

Hi Guys

Thanks for the feedback, did a check of all the hoses and true enough I connected the vac hose wrong. Connected it to the petcock down pipe instead of the vacuum valve which is at the back and towards the 9 o'clock position when looking from the front.

She is revving like a champ now.



Thanks for all the help.

Kit

[adewhitmarsh]

After stripping it all down you should have fitted manual ccts.

[bigtwinthing]

After stripping it all down you should have fitted manual ccts.

+1 on that. Bit of a waste of time really.

[8541Hawk]

I don't know.....sometimes the auto units can work ok......

[bigtwinthing]

I don't know.....sometimes the auto units can work ok......

yep just up until they let go at 8000 revs