Ticking after BBK install... Piston ring or valve spacing?

[lunatuck]

Just installed my BBK on my 4 stroke 50cc scooter.  It was a Goofit 50mm.

After first startup, I'm getting a ticking sound.  There were two places I had slight issues, so I'm hoping someone may have some ideas as this is my first BBK install.  I took a 5m ride at 1/4 throttle, but it still ticked. 

First, when assembling the piston with rings, the rings seemed very tight in the piston.  I checked a (broken in)2-stroke head I had, and it was not nearly as tight, but it only has two rings as opposed to the three.  I'm wondering if a new cylinder/piston should be so tight when new.  I put some motor oil into it and was able to slide it up and down in the cylinder, but it took some force.  I also noticed that when I turned the fan (timing mark)there was more resistance then before the BBK, but on a broken the old motor.  It felt like the piston rings were tight in there.

Also, the BBK came with 64mm valves, my scooter had 69mm valves; so I had to switch my rocker arms to the one with the kit.  I used a feeler gauge and set them to .004, but the bottom one was really tough.  It could be off, but probably not much.  Wouldn't a maladjusted valve spacing cause a ticking? 

Thanks for any help. 

Ugh...  Now it won't start and its kind of whining.  Starter is struggling.  Leaning towards piston issue, but maybe just battery dying and started struggling due to bigger cylinder.  I'll have to work on it tomorrow rather then riding. 

[benhonda]

too much valve lash will cause some ticking for sure
too much valve lash on the exhaust could make it hard to crank and cause it to run rough at higher rpms...basically not opening the valve enough and making it hard for the motor to breath properly.
Hopefully it is a valve lash issue and not the rings!

[lunatuck]

Well, its hard to start, but I also noticed some backfiring through the carb. Thinking it may just be valve lash.

Here’s hoping.

Hmm. Looks like I’m going tonspend my morning fishing a valve bolt out of my case.

[lunatuck]

Aaannndd fixed! Got my 3x 1/4 throttles and am up to my 3x 1/2. It already feels faster. Valves are pretty quiet, but not silent. I think thats right.

[GrumpyUnk]

I did not understand the 64mm vs 69mm thing... You can't mix and match the cam followers/rockers and valve stem length. That said, did you check ring end gap before you put things together? Normally, new rings will have LOTS of tension and scrape against the cylinder wall. That is normal. You should feel the increased friction as the rings rub into the bore. When you put it together, you want to put as much oil onto the rings as will stay. The engine will get rid of the excess within a short time once it starts. Same thing on the piston as you assemble it. There is no such thing as too much oil on a new assembly, piston, rings and cylinder.
Too much valve clearance will not only cause noise, but will reduce valve lift and duration. It will reduce power output to some degree. You want it 'like a sewing machine' as far as valve tappet noise. IMO.
If you did not check ring end gap, you may find that the rings expand and get jammed into the cylinder when they get hot. I have had to adjust the clearance on multiple ring sets. You can successfully remove the BBK and check the gap if you feel it necessary. You should replace the gaskets as you do so, but may get by without for some gaskets. Head gasket not a likely success point.
tom

[lunatuck]

Sept 17, 2019 22:39:45 GMT -5 GrumpyUnk said:

I did not understand the 64mm vs 69mm thing... You can't mix and match the cam followers/rockers and valve stem length. That said, did you check ring end gap before you put things together? Normally, new rings will have LOTS of tension and scrape against the cylinder wall. That is normal. You should feel the increased friction as the rings rub into the bore. When you put it together, you want to put as much oil onto the rings as will stay. The engine will get rid of the excess within a short time once it starts. Same thing on the piston as you assemble it. There is no such thing as too much oil on a new assembly, piston, rings and cylinder.
Too much valve clearance will not only cause noise, but will reduce valve lift and duration. It will reduce power output to some degree. You want it 'like a sewing machine' as far as valve tappet noise. IMO.
If you did not check ring end gap, you may find that the rings expand and get jammed into the cylinder when they get hot. I have had to adjust the clearance on multiple ring sets. You can successfully remove the BBK and check the gap if you feel it necessary. You should replace the gaskets as you do so, but may get by without for some gaskets. Head gasket not a likely success point.
tom

Thanks. The noisr was the valve spacing. The lock nut on the valve came loose. I tightened it up and have been riding it.

The rings spacing/gap seemed fine. I was overthinking the piston. It moved better when well oiled.

I am loving the new kit. Much faster all around. Especially on the hills. I am pulling up my troublesome hills at the speed limit!



The valve thing... the kit came with a 64mm valve head. My scoot had 69mm stock. I had to put the rocker arms from the kit onto the stock rocker base to install it on my kit head. I did all that correct, just didn’t tighten the valves enough after setting the lash.