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Honda bf25 question

P

posc

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Hi i have a Honda bf25d4 2004 and i want to convert it to a bf30. For what i see on Honda parts website they have the exact same parts except for the cdi unit the main jet and main nozzle and the camshaft , but i have a doubt for the camshaft !
Do anyone know if the camshaft is really different or they are the same thx

and i’m looking for a shop manuel if anyone got this that would be nice :cool: thx!!
 
Actually, the camshaft is probably the main component difference for the 30 hp to be able to effectively burn the additional fuel needed to provide the increase in power.

The 30hp cam opens the valves in a slightly different way vs. the 25hp. This is usually expressed as cam lobe lift and or cam lobe duration. Those two things affect valve timing and the engine's ability to "breathe in" more fuel and air mixture.

I believe if you simply add the larger volume fuel delivery components and CDI you will likely end up with something closer to a very inefficient 18hp engine that is sluggish and smokes because of the camshaft mismatch.

I have no technical documents to back up that assertion but I've been well trained and worked on engines my entire life. So....you"re just getting my opinion on the matter.

Good luck
 
I have never seen one of these type "upgrades" work well enough to warrant a prop change. Where the "new" motor over revs the original prop.

If the "new" motor DOESN'T over rev the original prop, it's not making any more power. It's that simple.....
 
Alan Hicks said:
I have never seen one of these type "upgrades" work well enough to warrant a prop change. Where the "new" motor over revs the original prop.

If the "new" motor DOESN'T over rev the original prop, it's not making any more power. It's that simple.....
Click to expand...


I will change the propeller too and this case !!
 
Well, without any engineering drawings or doing some very precise measuring you're likely not to discern any differences between the two camshafts just by looking at them. A simple protractor probably wouldn't suffice to measure for the very subtle timing differences although a good micrometer might readily reveal any lobe height changes.

Also, you should verify that the valves, rocker arms and cam bearings are exact matches too.

Good luck
 
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