Dynojet A/F Meter

[brewsky]

I know I'm probably beating a dead horse here, but my whole point in trying to find out the value of "H" was to put to bed the question of where to measure the float height from....gasket surface or body notch. If we knew the actual fuel height required, then the float measurement wouldn't matter as long as it resulted in the correct fuel level.

I believe "H" is the design value for the fuel height which probably was initially calculated, and then refined by testing by the carb design engineers. I realize it is probably designed for a specific altitude (or barometric pressure), temperature, humidity etc....so maybe it would be a "starting point" for adjustments for different conditions.

I guess it's also possible that the fuel level should remain constant, and the other variables (ie jets, needles, screws, cutouts etc) should be adjusted instead.

I don't know for sure how big a deal the 1.75mm difference in float adjustment is (difference in gasket surface vs body cutout measurement method).....but I do know for sure a 4mm difference is HUGE, as I initially was setting my PW22 carb to the wrong (PW26) spec. and it would barely run.

[brewsky]

Hi,


The fuel standard level is given in the same picture (nr. 6) so what is so difficult and mystery about it ? If h is 26,5 mm, then H is 18 mm or 0.709 in. Or you could say that the fuel level is 2 mm below the float bowl gasket face.

Jensen

Where does the 18mm value come from?

[Wilf]

brewsky,

My guess is that the 18 mm comes from measuring the distance from the carb bore to the bottom of the float and then subtracting 26.5 mm from that. If this is the case, it is no more accurate than using the 26.5 mm value 'h'.

jensen,

Ouch! I thought I was reading the manual correctly when I stated earlier that 'h' was given as 26.5 but that there was no value in the manual for 'H'. Brewsky was asking for 'H', you replied with 26.5 mm, and I offered my interpretation of the manual.

In addition, some float height diagrams show different measurement points for 'h', so any confusion is certainly honest.

teazer,

I do agree--LM's eyeball method works just fine, and any fine-tuning beyond that is subject to the individual machine/operator/environment...

Wilf

[jensen]

Hi,

That's the fuel level (plus or minus a mm) when h = 26,5 mm.

Jensen

[brewsky]

Hi,

That's the fuel level (plus or minus a mm) when h = 26,5 mm.

Jensen

Jensen, did you measure the 18mm or calculate it?

My whole point is the value for the fuel level will depend on where you measure "h" from.

Wilf:
"H" and "h" are confusing as they represent two different things in different diagrams.
If you notice one of Jensen's attachments labels the float height "H" and doesn't show the fuel height at all. It does show the notch or cutout in the carb body though and is the first diagram I've seen that does.

The other diagram shows "H" as the fuel level and "h" as the float level, but shows no cutout in the carb body. That is the same diagram as in my shop manual.

I could find no time when LM indicated the line of sight method applied to Dream carbs.

I can say that IF the correct reference for the 26.5mm is the cutout, not the gasket surface,....THEN the line of sight method does apply to a dream carb with cutouts.

See last 2 attachments here:
http://www.honda305.com/forums/viewtopi ... 6&start=10

[jensen]

Hi Brewsky,

Now I understand the mix up h and H. The first illustration at page 5 of this thread is from a CB450 K0, and it was displayed to show that the parallel thing is in all Honda carbs. The second illustration on page 5 of this thread is from a PW22 carburettor from a CB72, again for displaying the parallel principle. the third picture on page 5 of this thread is from also from a PW22 carb, again, the parallel principle.

However, to show that Honda isn't consisted in the use of h and H, and to show that Honda defines different reference surfaces, I showed both pictures ((please loo closely at the first illustration at page 5 of this thread, the CB450 K0, and compare that to the illustration on page 6 (PW22 carb). Now look VERY GOOD at the arrows, and what reference surface they use, now you know why there is so much misunderstanding of the reference surface (for easy comparing I expended both images). Honda CB450 reference surface is the cut out, PW22 reference surface is the lowest point on the carb body at the surface, so not the cut out, and not the gasket surface.

Now your question : where comes the 18 from ?

A:

I couldn't stand the talking and I measured it at my carb, btw, the parallel method is also correct, did you already looked at it ?

B:

Compared it to the drawings from Honda from the carb, it's drawn to scale, so it's easy determine.

Jensen

[Wilf]

brewsky,

Yes, that is exactly my interpretation of the situation and the diagrams.

Wilf