Motoscrubs.com

I am thinking about doing a carb swap on my 250 Mark3 NC and using a 30mm Dell Orto PHBH from Bevel Heaven. The carb looks like it will fit right on the intake spigot. Has anyone used this carb on a narrow case bike? Does the little choke lever clear the frame backbone? Are there any other issues with doing a straight bolt-up on this carb?

Hello Chuck,
I have a Mach1 replica with a 350 head (big valves) and big cam & compression with a quite muffler. The jetting I found for the 30mm PHBH is
Main 137
Pilot 45
Air correction jet 100
Needle X22 Leanest position
Jet Needle 262P
Slide 3.0
Trumpet 60mm
Sorry for the Mikuni names, old habits
It starts very good, runs perfectly to 4500 and perfectly after 5500 to over 8000. My intake port is too big for the engine to run well at 50 to 55 mph range. The carburetor is jetted as well as it can be. Many hours & dollars have been spent refining to this point. If you have a standard port size I think the carb will be magic on your bike
Al

[quote= alno ...
" I have a Mach1 replica with a 350 head "

____ REAL 350-cyl.heads are rare. _ They have a combustion-chamber OD of 76mm, while most cylinder-heads found on 350-models -(all w-c.versions) are actually large-valve type 250-heads with a 74mm-OD.

Dukaddy-DUKEs,
-Bob

Al,
Thanks for the info. I think I will go ahead and order one. The bike runs well on the SSI but one gets tired of chasing the adjustments for idle and dribbling gas while tickling the carb on startup.

Bob,
By 76mm and 74mm do you mean the outer edge of the squish area? Is there any benefit to the larger 350 head? I do have a couple of 350 heads in the pile of spares that came off NC motors. I should probably check them.

Dribbling gas is all part of the starting ritual. Sure its bad for the environment, but how else are you going to clean the engine cases if you are not wiping up spilled fuel? All kidding aside, I ran a 250 with that set up for a while and it behaved very well. You may have clearance problems with the carb using the stock manifold. Worst case you could use an RT manifold or make your own. Several venders sell the base plate and mooting piece un-welded for just such a situation.

m82a1 wrote:Dribbling gas is all part of the starting ritual. Sure its bad for the environment, but how else are you going to clean the engine cases if you are not wiping up spilled fuel? All kidding aside, I ran a 250 with that set up for a while and it behaved very well. You may have clearance problems with the carb using the stock manifold. Worst case you could use an RT manifold or make your own. Several venders sell the base plate and mooting piece un-welded for just such a situation.

Thanks for the info. I will probably try to install it next weekend.

Moto Chuck, if you're still out there how did the install go?