ruckus exhaust valve leak

[houstonpro]

Hi everyone
I bought a 2006 ruckus and it ran fine for a few months. Now after a new carb,piston and rings,new cam, valves and shims. I still have low compression 60psi. The bike starts and idles but will die if I give it throttle. I've done a compression leak down test and found that the exhaust valve is leaking. I've checked timing, valve clearance, TDC. Any ideas of what it could be?? Anything would help

[Baizy]

Hey houstonpro sounds like you've done a lot of research and checks already. Sorry to say but if after all that work you've got a leak from the exhaust valve you've probably got a bad exhaust valve seal in the head. I do want to ask right away though: Are you doing the compression test at wide open throttle? I've forgotten to do that myself and it usually leads to VERY disappointing compression numbers. If that solves compression then I'd suggest an ECU reset as your throttle position sensor might be out of whack causing the engine to die under more than idle conditions. Hope this helps, looking forward to hearing back!

[houstonpro]

Yes I've done the compression test with full throttle open. I've put oil down yhe cyclinder head and I'm didn't change compression. Meaning that its not yhe actual piston. So here's a question if my carburetor is not tune right could that cause bad compression? I mean its where air and fuel get mixed so could it affect the compression in the cyclinder??? The bike starts up fine snd idles fine. But... when I give it throttle it'll bogg out in mid throttle. I'm considering going bk to the stock jets and moving the needle back to #2 position.

[houstonpro]

Also what would cuase a bad exhaust valve seal?? Its got new valve, valve spring shims are to spec. New cam. I've looked for cracks or leaks in the actual casing but don't find anything. All new seal and gasket kits. I just have no idea what rose it could be

[Baizy]

A valve can have a bad seal if it wasn't seated properly when installed. You generally lap a valve prior to installation and that creates the best seal possible between the valve and the head. Look it up if you don't know much about it and you'll find lots of info out there!

[Baizy]

If you have a 2006 carb you shouldn't have different clip positions on the needle, are you sure you have the factory carb?

[houstonpro]

I used a valve lapping tool and lapping compound on new exhaust and intake valves. As far as the carburetor its a aftermarket carburetor off ebay. It has the both high and low jets. And it does have a needle w a C clip and five different positions to set the clip.

[houstonpro]

Ok. So after some research it appears that yhe harbor freight compression testers don't work. Usually only showing 50% of actual compression. So tmrw ill go and get a better compression tester. That would explain why the ruckus does start up with no problem and does run but bogs in mid throttle. Given me the idea that it maybe a carb adjustment issue. But.. it still can be a exhaust valve not fully closing

[Baizy]

I will take photos of my setup later today day for the carb. We likely have the same one and I can give you some tips on tuning it.

I've had a cheap compression tester fail after 8 cylinders so you could very well be right about the gauge being junk!

[houstonpro]

Yeah man please give me some tips on yhe carb tuning. And lmk what jets work best for you

[Baizy]

So a little forward before you straight up copy what I did I have a 58cc Ruckus with a Posh CDI, "custom" intake made from 1.5" rad hose and a K&N filter, Leo Vince exhaust, and a 20mm carb meant for a gy6 (same as the scooterswapshop 20mm carb). So I have no rev limit and a very free flowing setup. I'm not even done tuning it yet as it involves copious amounts of trial and error. I'll be posting the reply in multiple messages due to photos and time restraints. 

Here is my Ruck in progress:



It's a good ol' fashioned mix and match of stuff I found for cheap and cobbled together.

[Baizy]

This is the very messy setup I have tucked under my seat. Note the clear coolant line up front as you likely had to do the same thing when you swapped carbs. The other line is my fuel line, extra long so that I can install my stretch kit someday.



The carb came with 2 unmarked jets installed and I haven't swapped the slow jet yet and it is just horrible to start and it seems VERY LEAN my O2 sensor has indicated 15.5:1 which confirms the lean idea. The main jet I have in there right now is a 86. It was running pretty lean up top and rich on the bottom even with the needle leaned out but I THINK I FIXED IT. I'll give you the low down in the next post here. It's a little cheeky, but I am still led to try it out when the weather clears.

[Baizy]

So here's the cheeky thing I did today. 



Here are 2 carb needles side by side. The top needle is from a stock 2006+ ruckus carb and the bottom is from the 20mm CVK (note it has the different clip positions available) notice anything? They're the same length and diameter! Which means you can ALMOST swap them without any mods, the caveat to that being the stock needle needs the step right near the top removed so that it will fit insided the CVK's slide diaphragm and and the top ring thinned so that the retainer doesn't bend it over to a funny angle. I have access to a lathe which made this a very easy mod. Why swapping to the carb needle is so exciting for me is because with the CVK needle I had issues with it being lean up top and rich down low, a condition the updated stock needle was designed to fix. If it goes well in the tuning field I'll do a proper write up in the how to's as I have been dissapointed too often by a lack of aftermarket carb parts.