[Signore302]

Hello guys,
I’m new in this forum and I’m trying to find some correct info for these little bikes we like so much. Thanks in advance!
I’m struggling to set up properly the carbs. The mixture is rich as the plugs are soothy. She idles and runs good till the engine warms up, then lacks of power and even cuts down after a nice blast. Definitely the bowls are getting empty after the blast. The carbs has 98main jet and 38slow jet. Any of you guys know for sure the specs for the jets? I’ve found info online of people saying 90/38, 90/35, 98/35, 98/38. But I think the correct ones are 92/35 haha sounds crazy though. Anyway, I still have to play with the float and float valve but I’m sure there is more than one problem. All setup as follows:
Valve gap 0.05mm cold
Points: 0.35mm
Engine timming ok
Float level: 21mm from base
Petcock /carbs cleaned
Plugs: 0.65mm new
Compression: 8 bar( a bit low)

Well, we go from this guys!
Thanks Everyone

 

[Richard_Pitman]

There should be a number stamped on your inlet manifold flanges. CB175K6 should have 98 mains and 38 slow jets, 306B stamped on the manifold.

See this table ( when the photos are working again )

 

[Signore302]

Hi, thanks for you post. I’ve looked my manifolds and they are 644A, both of them. Does it changes the jet’s sizes? Cheers

 

[Richard_Pitman]

According to the table which we can't see , 644a carbs should have 90 mains, 38 slow, needle on 4th notch from the top.

 

[Signore302]

Just an update. My main jets actually are 90. The stamped number is a bit faded so I thought they were 98 but no. Also my float level was too low cos I was measuring 21mm from the edge and it should be from the base of the carb without gasket. Found this information online, forgot where sorry. It was a picture of the workshop manual. Now she runs much better than before. When I stripped the carb first time I measured the jets and I forgot the sizes but I think the 95 gauge went in the jet, suggesting that somebody has been playing with them before but I don’t remember very well haha I will do it again and make sure they are 90. Also the last time I measured compression it was 7bar... I’m planing to take the engine off, hone it and fit new rings. The needle is in the 4t notch. Thanks for the help guys!