1700 engine issue?

Hi all, just had my valve clearances done on my 1700 t4 engine and my mechanic friend has made me aware of an issue!

It seems that cylinders 1 and 3 are not doing a great deal on ticknover. When removing a plug lead to 1 or 3 this only has very little effect, like marginal to the running. If you remove 2 or 4 plug lead it noticeably runs on 3 cylinders.

He has done a compression test and all seems within limits.

Any ideas please??

 

What Carbs do you have attached. Twins???

 

Yeah twin Weber 34

 

It most probably is either a poorly adjusted carb or the carb needs a good clean. The idle jet is probably blocked.

Also have you got a balance pipe fitted?

Doe the engine pop or backfire?

 

To be honest I don't know if it has a balance pipe. I'm a bit of a novice

It does pop a little but not much. Haven't considered the carb as such because it only seems to be bad on 1 and 3. My mechanic seemed a bit confused by this and pointed to it maybe a worn camshaft? I am hoping it's something a little more easier...

 

Worn Camshaft normally would affect both sides of the engine. In fact I am almost certain on that.

The carb on the bad side I would first screw in the idle mixture screw and see if it causes the engine to stall. Wind it out slowly and if it has no effect then you can be certain it is a fuelling issue.

Personally I think you are best off ripping off the carbs to clean them. Also check the plugs are correct and pull one out and check they are sparking normally. In fact pull the plugs and take a picture as it is quite a good way to diagnose the engine.

 

Thanks Patrick

Not sure if I have this wrong but it it is both sides of the engine near the fuel tank. I have tried the mixture earlier tonight. Turning in does stalll the engine.

The mixture screen is about 2.5 turns out.

Plugs are the Bosch ones with blue stripe. Can't remember the specific one

 

That is a very sooty plug, implying you’re running rich. Do they look like that after a long run?

 

1 and 3 do share cam lobes... but I'd check spark then carb first if compression was ok and valve timing were done ok..

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That's what I thought...I have leaned it out and they do look better after a run.

Plugs are the WR7CC

Thanks

 

Thanks. Getting a spark ok. Although when i pull the lead off 1 and 3 it is hardly noticeable. Looks like the carbs to check next.

 

Oh I read this wrong. I thought one side was not working. So could still be a flat cam, but that is easy to diagnose as the tappet adjuster will be noticably screwed in further than the rest.

Without a balance pipe the engine the engine only idles on 2 cylinders as per your problem, but drives absolutely fine off idle.

 

Thanks for the reply. See photos of the carbs if this helps?

 

Looks like your filter could do with a clean out .

 

Yep no balance pipe. All the balance pipe is a 10mm hose that connects the two manifolds together. The hassle is removing the manifolds and either JB welding and tapping a hose connector on them.

The balance pipe has the magic effect of allowing the engine to idle on all cylinders at idle. I was told that without the balance pipe the engine would only idle on 2 cylinders.

I assume you have no brake servo.

 

Adjustment is on the heel of the cam; it’s lobe lift you need to measure to check for a flat cam. It’s easy enough to measure the valve lift and calculate the lobe lift (a Type 4 has 1.3:1 ratio rockers) but you need to know what cam is in the engine to know if it’s worn.

 

Get rid of those pancake air filters and fit some decent ones and fit the correct size hose clip on the crankcase breather. And fit a set of NGK plugs.

 

Thanks, I will need to look this up as I'm not sure on how to connect this up

 

Thanks, no idea what cam is in the engine