Sloper S30-13 performance issues

[Mike Farmer]

 

The only other thing that comes to mind is whether the Mag is actually going to fully advanced. Because less than fully advanced would possibly give the fault that you are experiencing.

Mike

[idie]

All this is very interesting. It sounds like lack of fuel. When my Velocette Viper did the same thing ,I found that it was ok with both taps on. On investigation I found that there was a poor flow threw both taps. A drill sorted that out. I know you most likely only have one tap but is the flow enough to keep up with the engines demands Also try a larger main jet even if it is out of spec.

[Gadorey]

At the moment, fuel flow really could be my main suspect. I shall try to set up another petrol tap with a larger diameter fuel line and test it. Perhaps the tap I have or the copper pipe to the carb are too restrictive. Both are not original and the copper pipe I did myself.

[Gadorey]

Here's a pic of my tap and petrol pipe.

[JohnCH]

The fuel filter inside the tank could also be clogged. Unbelievably, I once found a tank that was Petsealed with the filter still in place. Before fitting new parts I would just disconnect the copper pipe and measure the flow rate out of the tap.

[Gustafsson]

Have You checked the camlift?

[Gadorey]

Have You checked the camlift?

I haven't. Is there a reference value?

[Gadorey]

Today I was finally able to do another test run with a larger fuel line. No luck. Still the same.
Next I will try advancing the ignition some more, even though it is set by the book -points just opening at TDC, fully retarded. Running out if ideas here.
Cheers,
Gui

[Gadorey]

Another test run after advancing the timing a bit. She seemed happy with it and the acceleration was a bit better, but still no change in top speed. Just doesn't go much beyond 80kph or seem to have power at the top end. Since I opened the timing chest to adjust the ignition timing I also rechecked the valve timing just to be sure, and yes, all the markings were lined up properly.

[idie]

Are all the marks correct. Can you check them with a degree disc or by substitution with other cams. Difficult I know with such an old machine.

[Gadorey]

So I checked the valve timing today.

The exhaust timing is by the book - opens at 60 deg before BDC and closes at 20 deg after TDC.

The inlet is another matter. It opens at 40 deg before TDC and closes at 75 deg after BDC.  It should be 24 deg and 65 deg respectively.  So the timing marks are correct but it seems the cam profile is wrong.  Perhaps it was reprofiled at some time in the past, but not done correctly. The way it is, the inlet valve is opened too long.

I increased the inlet valve gap and did a test run, but made no difference. Above 80km/h there is not much left.

Last thing to try will be a larger main jet, but I'm losing hope now.

[idie]

It is a long way out the inlet timing seems that a lot of the charge is going out of the exhaust. I wouldn't have thought increasing the valve clearance would help it might change the timing but you lose the lift. Maybe you can borrow a cam from someone.

[Gadorey]

Final test today with a larger main jet. Went from a 160 to a 170.  Also no difference in the top end. 

[Gadorey]

I may have found the cause for the lack of performance. Following a suggestion to check if the slider was opening all the way (it was) I noticed the jet block made a step on the carb's throat. Disassembled it and sure enough it's a 15/16" jet block and not 1 1/16" as it should be. Further it has a 39 stamped on the top side and a 30 and a 0 on the bottom - not sure what this means. The question now is where can I get a 1 1/16" jet block for a 6/024 Amal? I checked some blocks for later 276's but the holes on the sides are completely different.

[idie]

When I checked my sons Shooting Star I found the same thing on a monobloc carb. I know it's not original but can you not fit a later 276 carb on as a temporary measure.