Stock Skorpion carb modification
Posted: Sun Apr 22, 2007 12:57 pm
FACT:
The Dyno does not lie. At sustained high revs the stock Skorpion carbs cannot supply enough fuel to the bigger carb. I hesitate to use the word sustained because the bike runs lean off the chart in just seconds. Most of the people on this forum understand that running this lean leads to burnt valves and burnt valves don't form a proper seal in the valve seats and now you are losing precious horse power. I'm no superstar mechanic but I get the concept.
OPINION:
For street use only, stock carbs are okay. The only mods to my Skorpion Sport Cup are the removal of that micro screen filter, a clip moved on one of the needles and an in line filter.
For street use and the occasional track day. I feel you have to make the fuel delivery mod that I have pictured. The extra transfer tube has proven itself on three different Skorpions on the long front straight at P.I.R. I'm not even sure this is an original idea. I think if you ask some of the guys who used to run the Yamaha SRX600 at the track they'd say that they have done the same type of mod.
For the track, you know the answer. Flatslides are great for creating top speed when jetted correctly. Having said that I'll admit that I don't use them. I like my Keihin 33mm smooth bores. They are beautifully made. They are a big jump in performance over and stock carb, modified or not. And I wouldn't be surprised if they work better than Flatslides on a tighter track with shorter straightaways. I have no experience on that type of course.
BANG FOR THE BUCK:
If my Skorpion was going to do double duty as street bike and track day bike I'd go with the modified stock carb. I just can't justify the extra expense of an after market carb for track days. Even if you did go high dollar on your street bike and put Flatslides on it would they work very good at low revs? I don't think so.
PARTS FOR MOD:
(1) 1/4 by 28 Tap
(1) 7/32d rill bit for tap hole. Opinions vary, make your own call on bit size.
(1) Drill bit for opening up the unused spigot on the carb bowl. I'm sorry I have no notes on the size I used. Make your own call.
(1) Tube of two part epoxy suitable to exposure to race gas.
(1) Napa Auto part #1410 brass elbow fitting. I hope they still have these listed under this number.
(1) Short length of appropriately-sized fuel line.
(2) Small hose clamps.
In my experience this modification goes a lot smoother with beer, a good friend and the optional bike race playing on the DVD. Time required is directly related to beer consumption. Private message me if you prefer to have me do the work. You can send me your carbs for mod but I'd rather sell you a modified carb complete. That way you don't have to go without your bike while you wait for me.
Regards, Jeffrey
[/b]
The Dyno does not lie. At sustained high revs the stock Skorpion carbs cannot supply enough fuel to the bigger carb. I hesitate to use the word sustained because the bike runs lean off the chart in just seconds. Most of the people on this forum understand that running this lean leads to burnt valves and burnt valves don't form a proper seal in the valve seats and now you are losing precious horse power. I'm no superstar mechanic but I get the concept.
OPINION:
For street use only, stock carbs are okay. The only mods to my Skorpion Sport Cup are the removal of that micro screen filter, a clip moved on one of the needles and an in line filter.
For street use and the occasional track day. I feel you have to make the fuel delivery mod that I have pictured. The extra transfer tube has proven itself on three different Skorpions on the long front straight at P.I.R. I'm not even sure this is an original idea. I think if you ask some of the guys who used to run the Yamaha SRX600 at the track they'd say that they have done the same type of mod.
For the track, you know the answer. Flatslides are great for creating top speed when jetted correctly. Having said that I'll admit that I don't use them. I like my Keihin 33mm smooth bores. They are beautifully made. They are a big jump in performance over and stock carb, modified or not. And I wouldn't be surprised if they work better than Flatslides on a tighter track with shorter straightaways. I have no experience on that type of course.
BANG FOR THE BUCK:
If my Skorpion was going to do double duty as street bike and track day bike I'd go with the modified stock carb. I just can't justify the extra expense of an after market carb for track days. Even if you did go high dollar on your street bike and put Flatslides on it would they work very good at low revs? I don't think so.
PARTS FOR MOD:
(1) 1/4 by 28 Tap
(1) 7/32d rill bit for tap hole. Opinions vary, make your own call on bit size.
(1) Drill bit for opening up the unused spigot on the carb bowl. I'm sorry I have no notes on the size I used. Make your own call.
(1) Tube of two part epoxy suitable to exposure to race gas.
(1) Napa Auto part #1410 brass elbow fitting. I hope they still have these listed under this number.
(1) Short length of appropriately-sized fuel line.
(2) Small hose clamps.
In my experience this modification goes a lot smoother with beer, a good friend and the optional bike race playing on the DVD. Time required is directly related to beer consumption. Private message me if you prefer to have me do the work. You can send me your carbs for mod but I'd rather sell you a modified carb complete. That way you don't have to go without your bike while you wait for me.
Regards, Jeffrey
[/b]