Oil Pump Mod

was having a ponder last night about the oil pump on the ole VF. I’ve got a Dave Dodge Mod Kit to fit, but after staring at the motor for a bit I thought to myself, why not increase the rate of flow from the pump. It’s chain driven by a simple sprocket on the pump shaft. Why not alter the gearing by fitting a smaller driven sprocket on the pump, thereby increasing the revolutions of the pump shaft in relation to the drive sprocket? OK the drive chain might have to be shortened by a link or two, but that wouldn’t be too difficult and a smaller sprocket wouldn’t be a problem to fit in the space where a larger one once sat.
Anyone know a reason why it hasn’t been tried/wouldn’t work?[?]

Hi Scratcher,
I’ve been thinking the same thing for a while, I did read somewhere on one of the forums of a guy who had turbo charged his vf1000 and had altered the oilpump gear drive ratio without any reported problems.

As far as I can see, it would just reach max oil pressure lower in the rev range, the oil pressure relief valve would still govern the max pressure/oil flow. This mod should give more pressure/oil flow in the reported problematic rev range. ie idle to 2000rpm.

The load on the drive chain would increase but for the amounts we are talking about I think it should cope.

I also remember reading that Dave Dodge can modify the VF’s oil pump although it didn’t say what the mod was.

Anyone got any other thoughts!

In theory you are correct but tread with caution. Oil pumps have a minimum and a maximum rpm that they are capable of running at, outside of which their performance is greatly impaired. (Excessive heat, stress etc.) The gearing will have been calculated on the pump manufacturers specs. Might be worth contacting a pump manufacturer for some specs.

Hmmm. Got me thinking has this. Think I’m gonna sit down and calculate the max rpm of the pump in stock form at max engine revs, then calculate the increase with a tooth less on the driven sprocket. I’ll also email Dave Dodge and ask his opinion and what his oil pump mod involved.

It might be worth taking a look at other honda V4 (400,500,750,1100)models to see if they had similar pump sprockets for varying sizes, maybe someone on this site have some kicking around, also as far as extra strain is concerned would it not make some difference if we are using modern synthetics, after all these engines were designed round 25 year old oil technology.