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#88943
Daiwiskers wrote:
Sat Apr 04, 2020 4:21 pm

I like a clear fuel line but it's proving almost impossible to find a clear line that will last (I have yellow Tygon on at present)
Try the red-stripe stuff they use on karts (mandatory in some formulas). It's called "freeline". Lasts well, not too expensive either.
#88947
Ordered

With a clear fuel line you can often spot fuel flow issues

Another thing that caught me out and I could have spotted easily was trying to set the carb up when the bike was just about to run on to reserve (Yup should have guessed but didn't)

And don't even ask about the on/off/reserve tap I once bought, the on/reserve position made no difference it would drain the tank when switched to on (I thought it was doing well on fuel)

Forgot to say running weak can be a cause of pinking

Edit
Sorry another question
Has the bike been stood for any length of time
#88981
Daiwiskers wrote:I have to ask how was it running before the 612 conversion?
Has it run right since the conversion?
my pinking problem was started when I changed gearbox sprocket 17 to 20

Let me introduce my bike history....

1. standard

2. 535 cylinder/piston with tuned cylinder head and 20t sprocket (pinking sounds start from this modify - but pinking is solved by retard ignition timing)

3. put on long stroke crank (with 535 cylinder so, now 612) (pinking sounds came up again)


However, yesterday I put in high octane gasoline, most of pinking problem has solved.

now I`ll try replace the spark plug. using champion or others by same level as NGK heat range 6.
#88982
A different gearbox sprocket won't cause the engine to predetonate. It may however be making you select an inappropriate gear for your road speed , encouraging you to ride with an increased engine loading.

Or outside possability, is this pinking at all? Or could it be some other sort of noise? Check the inside run of the chain for any witness marks where the ends of the pins might have hit something because a 20t sprocket will see the pins coming very close the the end of one of the crankcase studs.

This is how it looks with a 21t sprocket on mine. I had to make sure I had that nut near the very end of the stud then tighten it down from the other side :
Image
#88984
I still have a feeling that it's fuel related accentuated (that was hard word for me) by the high gearing
As Bullet whisperer said dropping to a 18 or 19 tooth gearbox sprocket would help, it would also make the bike a bit nippier
Most people seem to fit a decompression plate with the 612 conversion

Interesting that using higher octain fuel has helped, if you had half a tank then topped up with the high octain it might be enough to run high octain fuel
Some of the fuel taps don't flow enough fuel for a standard engine let alone a tuned one

Do you have a depth gauge? if so you could give us a measurement at TDC from the piston to the flat surface of the head, I am sure one of the people here can measure their's, this way we will know that the compression is in the right ball park, I wouldn't retard the inlet cam before I did this
It's difficult to try to diagnose without being hands on
It could well be something simple like carb slide or needle height
How's the plug colour ? if black it may be running very rich and washing the bore in this case your not hearing pinking but piston slap

Hopefully we can get you sorted without too much expense Dai
#89002
stinkwheel wrote:A different gearbox sprocket won't cause the engine to predetonate. It may however be making you select an inappropriate gear for your road speed , encouraging you to ride with an increased engine loading.

Or outside possability, is this pinking at all? Or could it be some other sort of noise? Check the inside run of the chain for any witness marks where the ends of the pins might have hit something because a 20t sprocket will see the pins coming very close the the end of one of the crankcase studs.

This is how it looks with a 21t sprocket on mine. I had to make sure I had that nut near the very end of the stud then tighten it down from the other side :
Image
As you said, now I`m pushing engine rev much more than before. and It is also helping reduce the pinking sound.
well, Now I know that 4000 ~ 5000rpm is suitable for peak output, but before that, very first time when I bought my bullet 2 years ago, my mechanic told me not to exceed 3000rpm, so I was afraid of that part.

After that, I rebuild the entire engine myself last winter to install the 612 crank. and I checked all of touching point such as bolt stud like your picture. you can trust me.

I think dropping sprocket is also can help reduce pinking sound to relieve the load. however it can solve by increase rev
and Current gear ratio is satisfying to me. so I would like to try another method this weekend. (ex. increase heat range of spark plug)

and this weekend I`ll do check my bike depth / spark plug condition etc.

thanks for read and helping me!

regards,

Lee June Woo
#89038
I just had a look at the 612 conversion
It's quite a bit more than barrel head piston and crank
It comes with compression plates, cams, and quite a few other bits and pieces if there's a critical part missing we could be in trouble
Perhaps a call to our host's is in order or perhaps a email to them
#89041
Daiwiskers wrote:
Tue Apr 07, 2020 4:09 pm
I just had a look at the 612 conversion
It's quite a bit more than barrel head piston and crank
It comes with compression plates, cams, and quite a few other bits and pieces if there's a critical part missing we could be in trouble
Perhaps a call to our host's is in order or perhaps a email to them
Yes, here are the inlet cams. Standard on left, tuning kit on right. Lift, dwell and duration all significantly higher. Alows it to guzzle plenty of go-juice.

Image

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