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PHM 40 float valve size

FrankG5

FrankG5

Just got it firing!
Joined
Sep 28, 2021
Messages
17
Location
Washington, US
I have 420 float valves in my carbs on my v1000. Seems they’re much too big, I’ve noticed after a run that there’s what appears to be fuel on the sidewall of my back tire. Going off the manual for the 40s what I’m experiencing matches what they describe for too large of a float valve. I don’t have any spares so I’ll most likely end up buying new ones after checking the float height just in case. I’ve heard 300 was typical for a big valve engine but don’t know personally. Does anyone have a recommendation in size?
 
FrankG5 said:
I have 420 float valves in my carbs on my v1000. Seems they’re much too big, I’ve noticed after a run that there’s what appears to be fuel on the sidewall of my back tire. Going off the manual for the 40s what I’m experiencing matches what they describe for too large of a float valve. I don’t have any spares so I’ll most likely end up buying new ones after checking the float height just in case. I’ve heard 300 was typical for a big valve engine but don’t know personally. Does anyone have a recommendation in size?
Click to expand...
Checking my DelOrto information, there are only 200, 250, and 300 float needle seats. Seeing a 400 is not right. I'd go with the 250 since you shouldn't have 40mm carbs. The V1000 you picture is not a big valve engine unless someone put in a MK IV or MK V LeMans engine. Those engines would have 40mm carbs.
 
john zibell said:
Checking my DelOrto information, there are only 200, 250, and 300 float needle seats. Seeing a 400 is not right. I'd go with the 250 since you shouldn't have 40mm carbs. The V1000 you picture is not a big valve engine unless someone put in a MK IV or MK V LeMans engine. Those engines would have 40mm carbs.
Click to expand...
It’s a small valve I believe. Original engine and all stock besides carbs and exhaust. Later I will post a picture of the current seats. I’m not sure what the carbs came off or what they were meant for if they were bought new. Dellorto shop has 2 options, one ranging from 150-225 and the other 250-400. I’ve never seen or heard of 420 seats except in mine. Would 300 be appropriate if I changed the camshaft later on?
 
FrankG5 said:
It’s a small valve I believe. Original engine and all stock besides carbs and exhaust. Later I will post a picture of the current seats. I’m not sure what the carbs came off or what they were meant for if they were bought new. Dellorto shop has 2 options, one ranging from 150-225 and the other 250-400. I’ve never seen or heard of 420 seats except in mine. Would 300 be appropriate if I changed the camshaft later on?
Click to expand...
Cam has nothing to do with the jetting/fuel delivery. It is a factor of the air pump efficiency of the engine. Also If you have 40mm carbs, they aren't original to the bike. Largest for that engine would be 36mm.
 
John, here are photos of the needle valve seat. I’m also attaching the link to Dellorto shop, in the description they direct you to another set of needle valve assemblies in smaller sizes. The bike came with 30mm VHBs and has had 36s, now 40s.

dellortoshop.com/contents/en-us/p4240_8649-Genuine-Rubber-Tipped-Needle-Valve-Assembly-for-Dellorto-PHM-carburetor.html

IMG 1028 IMG 1029
 
The 40mm DelOrto is way too big for that engine. Go back to the 30s if you can, or at least the 36s. There is a formula for carb sizing in the downloads. You will have to be running about 7,300 RPM for the carb to be at the efficiency level for your bore and stroke.
 
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