A
Anonymous
Guest
So I thought I'd bring everyone up to date on my adventures in carb tuning.
A little back ground is in order. This is a '78 1000 with a V&H 4 into 1, K & N filters and Dyna ignition and coils. The head has been ported and milled and has a pair of Mega-Cycle cams installed. Due to a massive over rev while drag racing and missing 2nd gear, the crank has been indexed and welded.
After numerous attempts at tuning with the Dynojet kit on my own, I became frustrated and took the bike to a reputable shop so they could sort it out. Unfortunatly their efforts were only marginally more fruitful than my own.
This bike ran like the wind at top end. How's a high 10 second quarter mile time sound. With the baffle removed from the exhaust, you could see flames shooting from the tail pipe. What a beast! Wheelies and burn outs with the mere twist of the wrist. How much fun can one person have?
The problem was, the drivability was for $hi#! While the overly rich idle circuit made the bike pull decent off the line the needles were so lean that adding a little choke was the only way to cruise along at respectful speeds. Think of the fun of driving up to a red light and down shifting, braking and turning off a carb mounted choke all at the same time. How many left hands does one man need?
About a month ago, Thunder Dan posted that he would like to take the leap into the dark world of pod filters. Oh you poor misguided man I thought. I could not stand by and watch another fellow GS'r go down the dark path. "Don't do it!" I cried. Save yourself from this tragedy.
Along comes Keith Krause. He says it can be done. He has obviously been sniffing too many exhaust fumes.
Well, to make a long post longer. There is this instruction booklet that comes with the jet kit. And buried deep in the booklet is a sentence that should be read and understood. It can be chanted as a mantra if you wish. For it seems these guys at Dynojet Research have a slight clue as to what they are doing. Yes, as amazing as it appears on the surface, they put a lot of research into their jet kits. Hence the second part of their company name. That one overlooked sentence that held me and a coulple of good bike shops back from making this sweet bike into a sweet driving ride.
"If your bike cannot pass tests 1,2 and 3, your machine may be running at less than designed efficiency." In other words, It's not always the carburetors stupid, check to see what else is messed up!
So with Keith's help and some adjustable cam gears, the cam shafts are no longer at the ridiculously high lobe centers of 117 and 115 degrees. Nothing like a stretched chain to throw things out of whack.
So, the point is, you can have a nice running bike with 26mm carbs and pod filters. It just takes some time to tune them in. Currently settings on my carbs are as follows. Pilot screws at 1 1/2 turns, idle air screws at 1 3/4 turns, needles at #4 position and 138 main jets. The bike runs well now. Not perfect, but worlds better than it was. The only real problem right now is a flat spot at 5000 rpm at wide open throttle. I'm gong to try the 142 main jets as it seems a bit lean at the top end as well.
Steve
A little back ground is in order. This is a '78 1000 with a V&H 4 into 1, K & N filters and Dyna ignition and coils. The head has been ported and milled and has a pair of Mega-Cycle cams installed. Due to a massive over rev while drag racing and missing 2nd gear, the crank has been indexed and welded.
After numerous attempts at tuning with the Dynojet kit on my own, I became frustrated and took the bike to a reputable shop so they could sort it out. Unfortunatly their efforts were only marginally more fruitful than my own.
This bike ran like the wind at top end. How's a high 10 second quarter mile time sound. With the baffle removed from the exhaust, you could see flames shooting from the tail pipe. What a beast! Wheelies and burn outs with the mere twist of the wrist. How much fun can one person have?
The problem was, the drivability was for $hi#! While the overly rich idle circuit made the bike pull decent off the line the needles were so lean that adding a little choke was the only way to cruise along at respectful speeds. Think of the fun of driving up to a red light and down shifting, braking and turning off a carb mounted choke all at the same time. How many left hands does one man need?
About a month ago, Thunder Dan posted that he would like to take the leap into the dark world of pod filters. Oh you poor misguided man I thought. I could not stand by and watch another fellow GS'r go down the dark path. "Don't do it!" I cried. Save yourself from this tragedy.
Along comes Keith Krause. He says it can be done. He has obviously been sniffing too many exhaust fumes.
Well, to make a long post longer. There is this instruction booklet that comes with the jet kit. And buried deep in the booklet is a sentence that should be read and understood. It can be chanted as a mantra if you wish. For it seems these guys at Dynojet Research have a slight clue as to what they are doing. Yes, as amazing as it appears on the surface, they put a lot of research into their jet kits. Hence the second part of their company name. That one overlooked sentence that held me and a coulple of good bike shops back from making this sweet bike into a sweet driving ride.
"If your bike cannot pass tests 1,2 and 3, your machine may be running at less than designed efficiency." In other words, It's not always the carburetors stupid, check to see what else is messed up!
So with Keith's help and some adjustable cam gears, the cam shafts are no longer at the ridiculously high lobe centers of 117 and 115 degrees. Nothing like a stretched chain to throw things out of whack.
So, the point is, you can have a nice running bike with 26mm carbs and pod filters. It just takes some time to tune them in. Currently settings on my carbs are as follows. Pilot screws at 1 1/2 turns, idle air screws at 1 3/4 turns, needles at #4 position and 138 main jets. The bike runs well now. Not perfect, but worlds better than it was. The only real problem right now is a flat spot at 5000 rpm at wide open throttle. I'm gong to try the 142 main jets as it seems a bit lean at the top end as well.
Steve
