Topic: HM300s on a K2

[mcswny]

Quick question. When I got my 750 K2 it had HM300s instead of what I believe to be stock for that year (HM341s). My gas mileage is alright 35-40 MPG and I my accel and decel are good. I'm just wondering if when the HM300s were put on, should my jetting have been changed? I've never broken into my carbs so I don't know the current jet size.

This is my first bike, so I am just wondering if I could increase the performance and tune by correctly jetting my carbs to the some-what-not-so stock pipes. Or just leave what's not broken alone.

[andy750]

I have a 1972 CB750K2 with HM300 pipes and stock carbs/airbox. My jetting is mains 120, pilot 40, forget the needle clip position but believe its stock. I tried main jets from 110-112.5-115-117 to 120 before I got it right (was getting popping on decel).

Check your jets by popping off the bowl on #1 or #4, try the exhaust and see how you get on then make changes if needed.

good luck
Andy

[edwardmorris]

Andy's jetting seems correct for HM300s (at least the 120 mains) IIRC, Hondaman mentioned that early K2s had 120 mains with HM341s and this ended up with a lot of spark plug fouling issues, so later K2s had 105 mains.

[mcswny]

I have a 1972 CB750K2 with HM300 pipes and stock carbs/airbox. My jetting is mains 120, pilot 40, forget the needle clip position but believe its stock. I tried main jets from 110-112.5-115-117 to 120 before I got it right (was getting popping on decel).

Check your jets by popping off the bowl on #1 or #4, try the exhaust and see how you get on then make changes if needed.

good luck
Andy

This is a better answer than I could have asked for because I actually am getting a little poppy on decel (forgot to mention)

Thanks Andy!!!

[mcswny]

Andy's jetting seems correct for HM300s (at least the 120 mains) IIRC, Hondaman mentioned that early K2s had 120 mains with HM341s and this ended up with a lot of spark plug fouling issues, so later K2s had 105 mains.

Thanks Edward, if I remember correctly I have a later K2 but can't verify till later.

Thanks for the input.

Tim.

[PeWe]

You'll get more for HM300 than HM341 if selling them.

[mcswny]

You'll get more for HM300 than HM341 if selling them.

Definitely not selling them, just wanted to see about my jetting on a K2 with HM300s vs HM341s

[Tews19]

I have 341s, let's trade!

[Roach Carver]

The hm300s are great. Much better pipe than the 341

[mcswny]

I have 341s, let's trade!

Ayah nice try tews!


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