[Erwin]

I am building a new engine for my CB350K3. Specs will be roughly:

• 67.5mm pistons (from Todd Henning Racing)
• Compression: To be determined, can be modified but I start at 11:1
• Carbs: standard
• Air filters: I'd like to retain the original filters but large pods or foam uni filters are also on the table
• Exhaust: David Silver OEM replica's
• Head: NOS head with stainless Schumann Motorworks valves and beehive springs
• Ignition: Charlies place electronic ignition with standard mechanical advancer
• Eaton oil pump
• Cappellini paper filter

Will this setup work with a 123-X5 Megacycle cam or should I aim a bit lower? Maybe the 123-20 is a better match.

As a rider I am willing to cope with some negative effects but I would like it to be somewhat ridable and practical. It is not a daily driver but I'd like to take it on weekend trips to the mountains. To compare, I used to ride a XT500 with 600cc cylinder, lightened flywheel and crank with a pretty ambitious camshaft and for me that was fine on the road.

 

[540nova]

I think Mikuni VM 30 carbs, along with a more free-flowing exhaust, but sized at 1.25", would work much better, especially if you are considering pods. I have a custom ground Megacycle cam, and found Megacycle a pleasure to work with.

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[Erwin]

My question was mainly about the cam in combination with the setup I have and not about changing the rest of the setup. I am not going down the route you suggest from the start. First I want to see if it can be made to work with the muffler I have. I'd like to keep the appearance as stock as possible. Stock carbs and air filters are really not that bad if you ask me.

 

[ancientdad]

Stock carbs and air filters on the 350 definitely aren't bad, but the pistons and cam change (no matter which cam you use) would benefit more from a small increase in carb size. Stock carbs are 28mm, bumping up to 30mm would allow greater volume of incoming air/fuel mix to match the better breathing cam and larger cylinder capacity, which would better maximize the capability of the performance parts installed. I understand wanting to keep the carbs and exhaust stock to be a bit of a "sleeper", but you won't get the full potential from the pistons and cams

 

[Joben]

Curious what cam you went with, I'm kinda in the same situation looking for the best cam option. I'm leaning more towards the megacycle 123-20 vs the 123-x5 since I'm going with 66mm pistons from Todd Henning.

Can't seem to find one particular thread with a 66mm set up.

Probably going to order everything through Todd Henning, so I'm sure they will point me in the right direction as well.

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[Erwin]

That is a coincidence... I ordered a X5 cam right this morning.