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Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by sakurama, May 5, 2009.
Tried this in two diff browsers, just got a jpeg.
Sorry, I linked to his gallery and he took it down. I think I saved them in my texts so I'll update the original post. NJ was hit hardest but NYC got walloped like I've never seen - from water. Planes are another story...
Sweet plan and soon, a happy birthday! I am sure Chris has had other matters to attend to, the power outage just helped "free" him from the shop. His projects will continue, all in good time.
When do you fly to NY? Really curious to see what you can do with 41's
No sweat. But ouch, those are painful pics to take in. Godspeed.
I'm finally back east and Chris finally got his final velocity stacks finished. He's also finished a TPS bracket and reduced pull springs. I shot some photos for his site of my carbs and I'm going to try to get them all mounted up this weekend and go out for a short cold ride to test them out. Finally.
They look bas ass ! ! ! .... did you get a chance to run the 41's yet??
They are some nice stacks. Are they the same profile as what you dyno tested?
Great work on the TPS mount as well. Any thoughts on a choke then you'd have it covered
Haven't gotten the chance to test the 41's yet. They're here but there were some replacement parts that were shipped via USPS that haven't shown up (lot's of delays with Sandy even now) so I'm hoping they show up by the weekend and I can give them a try.
I was considering getting the kit on the bike this week so I could just ride it around the city instead of take the subway but my registration is expired and of course the DMV is only open while I'm working and it's been really cold so I could really use a set of chokes on the carbs to make cold starting easier. Chris has been investigating the choke thing and he's aware that it's a real deal breaker for a lot of people to get the FCR's so I'm hopeful he'll work up a solution. It's still in the works.
The stacks are the same profile and length but the filter ring was moved below to help the whole thing fit under the seat. We're going to run my bike with the final part this weekend just to check it.
Excited to see the results of the package test.
The TPS unit is very nice and will be my next purchase.
Way cleaner and user friendly than my solution of replacing the entire pivot shaft with an extended one to drive the TPS.
Yeah, I was proud of my TPS bracket/solution but Chris' is very slick and requires only two holes to be drilled in the bracket. I'm going to use his version. Hoping to get it put back together for a ride this weekend. Sunday might be in the 50's so the bike should start fine...
In other news our shop is going through some changes and like it or not ill need to be moved out by the end of January. The good part of that is that I'm excited to get the 990 back to Portland - if ever a bike suited a town it that would be it. Of course the 990 will have to make the trip with a mill, lathe, and a few other bits and bikes. I'm really hoping we've closed on our house by then and I have a place for it all.
So the choke...
Well, there seems to be good news, bad news and no news which isn't necessarily good news. I'll explain.
Last night I made it to the shop after work and Chris and I sat down with his MX-FCR from his KTM 450EXC and my FCR downdraft. The idea was to examine each one to try to understand the choke (which is on the MX) and to see if the same circuitry exists on the downdraft so it could be "enabled". Here's a shot of the top of the MX carb's circuit with the choke plunger removed:
So the FCR actually has two main parts in the body. The main body holds the slide and the second part is the interface between the float bowl and the upper body. If you remove that part you can see the series of gaskets and o-rings that route the gas to the various passages. Here's the top of the lower part of the MX:
So the downdraft carb has the boss for a choke and it has the castings for the passages. The two parts are held together with security torx screws on the MX carb but are epoxied together on the downdraft. We spent a while trying to get the two parts apart and it's apparent that they don't want you to take the two apart.
Even the torch and a lead mallet weren't getting them apart. We could have persisted but there was the worry that if we did get them apart and they had used epoxy to separate the various ports and passages it would have been a nightmare to re-epoxy that all back together. The goal was to see if the passages had been drilled in the downdraft so that you could simply drill the top and bottom ports and then tap and install the choke. Since we couldn't get them apart we don't know but since neither top nor bottom was machined on the downdraft we can assume they weren't. Also, since the carb is epoxied together it is effectively impossible to retrofit the choke for anything close to a reasonable cost.
But it's not all bad news. The good news is that the actual casting has the potential for a choke. The bad news is that unless it was drilled by the Keihin factory before it was epoxied it would a nightmare to try to retrofit. The good news is that the velocity stacks project got Chris to be a Sudco distributer so he has contact with their tech department. He's going to ask if it might be possible to special order downdraft bodies from Japan with the machining operations for a choke made. If that was done he could customize his kit through Sudco to include a choke. So, it's possible. Just not for those of us who already have them.
Once we hear back we'll let you know.
So, that's the choke news.
You gots lots of patience!
Sorry if this is a noob question, but is there a great deal of difference performance wise between the 2 types of carbs?
Not a dumb question. The big difference is that the way the float bowls are positioned. You can't tip the MX carb onto it's side because the float bowl would not be level and therefore the gas wouldn't be and then it wouldn't work. The down draft carbs that the 950 uses have the float bowl positioned so they work sideways. Sadly though they don't have a choke but they have the potential for one - it might require a large order to have them specially made at the factory but the casting has the potential if they're interested in doing the post machining on a batch.
More bad news on the choke front from Chris today. He heard back from Sudco and they said that many people have tried to put chokes into the FCR's and no one has ever managed to do it. He also said that Keihin has no interest making it and won't even sell Sudco the internal parts. So bummer there.
Now this part might be good news: Chris managed to get my epoxied carb apart and discovered that the internals are similar to the MX with o-rings between the channels, passages etc. None of the passages are drilled of course. Chris thinks he could do the machining to make the choke fit and be functional but because of the huge amount of work involved it would cost between $250 and $300 but would include the cables, splitter, choke etc.
For those of you with FCR's - is it worth it?
Before we get too far along on our speculation we'd have to actually put chokes on my carbs and make them work. You never know if Keihin had a really good reason for not putting chokes on their carbs so we need to prove it can be done first. If it can be done, we need to decide (or rather Chris does) if it's worth the effort. And then those with the carbs would need to decide if it's worth the expense.
My sense of it is that Chris should go for it and offer a full kit with all the problems solved so it's a bolt on solution which will make it easier for those without the mechanical resources or skills. Thoughts?
Unfortunately i believe you can't buy the seal that goes between the body of the slant body fcrs and you can only get an aftermarket seal for the fcr-mx, it comes in a kit with a dual squirt nozle for a $100 or so.
And as far as i know the little seal under the Venturi ring is not available anywhere.
For the pair? Or each?
If for the pair, I'd probably spring for it - given how long it takes to get the CV-powered 950 running warm (ie choke can be turned off) in cold weather here....
BTW, the kit is looking very nice!!
Turn key for the nonmechanical would make the FCR's much more accessable. There would only be price resistance, instead of "will it start" uncertainty, after the solutions are in place. The value of the complete package speaks for itsself and there would be the addition of confidence in the system for a "street level" user.
Hope that choke solution is worth the development. I have fuel fouled plugs, with all the acc pumping I do to start up.
An additional consideration for choking:
Put the choke in the velocity stack!
Kinda against max dyno numbers, and you could say I stole the idea from briggs and stratton, but a razor thin flap on a pivot shaft, mounted through the velocity stack, would produce a true choke effect.
The tech way to do it would be to use a plunging guillitine that slides into the tract for choking and becomes flush with the I.D. stack wall when retracted. Like a power valve blade on a two-stroke exhaust port, only on the dry side of the intake.
This integration eliminates the expensive and risky(gotta source those internals) keihn conversation and becomes a matter of Chris and mastercam having a few beers together with the CNC.
More beers, and this issue will be choked, I say...
edit to add: It also adds a sku to the offering, choked or unchoked stacks?
And even the mechanical with limited time/resources....
1 by 1, some of the issues I had been looking to solve with the FCR's have been solve here in this thread
The only issue I have left to solve, when this kit becomes available, is some kind of 'airbox'. Just to give the whole intake side the same kind of resistance to water that the original airbox/snorkel had. I've actually laid the SE (with original airbox/CV's) over in shallow-ish water and was quite confident no water had gotten in...