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Dyno testing

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Liam:
Hi

Nearing the end of my build and one of the last tasks is to sort the jetting out Anyone recommend a dyno tester who could sort the jetting out on my bike...  usual mods which I inherited - pod filters and 4 into 1 exhaust.  I'm in the Saddleworth / East Manchester

Done the research and seems like a mare to get spot on...

The bike is a CB750F Supersport and I'm in the Saddleworth / East Manchester

Cheers

MarkCR750:
[ Guests cannot view attachments ] Hi Liam, I’m not local to you so I don’t know of any dynoes in your area, I have a K6 engine in mine with PD41a carbs/pod filters  and a 4 into 1, so it’s similar, I guessed my main jet sizes, went with 135 mains much bigger than the standard jet size, standard primary jets, needles on the middle notch, cheap Chinese pod filters , took it to Sam ermelenko’s dyno in Tutbury, fuelling was spot on, it ran great apart from it “surged” a bit when trying to cruise at a steady 70mph, I suspected it was the airflow into the carbs, if you look at the rubber bungs that hold the pods to the carb they have a square edge, the standard air box has 4 rubber velocity stacks, so I took the rubber velocity stacks off the original air box , removed the rubbers from the pods and grafted the rubber stacks in their place, problem solved, runs great through the range now and holds steady at any cruising speed, Honda didn’t go to the trouble of fitting the rubber stacks for no reason so my guess is they smooth the flow into the carbs and this aids carburation, I can’t find a photo of the mod I did but if you search on the forum there will be one in one of my threads. EDIT, you can see them on this photo .

royhall:
Just wondering Mark, how brutal were they at the dyno...... I went to look at a dyno test a couple of years ago (not my bike thankfully) and they revved the bike hard through all the gears...... The engineer said afterwards that you have to sign a disclaimer and they blow-up engines on a regular basis....... There was a large air fan in front of the dyno, but as they revved it out in top gear it should have been doing 120mph and the gentle breeze from the fan just did not feel enough to cool the engine. I don't know enough about dyno testing to say that it was a daft thing to do on an old road bike, but their not doing any of mine. I know you need to give it the beans to test it properly, but is this the normal thing or was it just this guy that was hard on the machinery.

Trigger:
I have been with Ralph Holland at MK Dyno a few times when he has blown up the customers engine in front of them. The customers face, when Ralf says, " well, that's what you just paid me to do"  ;D ;D ;D To dyno any engine it must be at its best in the first place ;)

Liam:
Thanks gents,

Roy, Trigger - very good point regarding full throttle through the range.  Unlikely I'll go through with it.

In the meantime Mark - I think I'll fettle the the main jet size and see how it runs / how the plug look.  Needle is on the middle setting, seems to tick over okay, no popping etc. but still have to balance the carbs.  You're right about the velocity stack in the stock air box...  Good ol' "Hondaman" gives an insight into the flow of air being patterned to prevent flat spots between the low, mid range and full throttle.  Unfortunately the bike came with Chinese pods which were split etc.  I swapped for "ramair" filters so no doubt will be dealing with at least one flat spot.

Cheers Gents

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