Snowmobile Parts

I’d kind of hoped that Erik Buell was from someplace in the Great White North.

Someplace where there are polar bears, and everybody call their snowmobile their ‘sled’.

Because if it was I’d at least have some way to understand the context for a recent brain puzzler that had my cerebral wires leaking smoke for the last couple of days.

But he’s from Pittsburg.

So I don’t.

 

***

 

I guess I could be underthinking this.

It’s not out of the realm of possibility that there might be a snowmobile or two in Pittsburg.

Your odds there have got to be better than Atlanta or Miami, say, but it’s not likely there are a lot of sleds there, compared with say, The UP of Michigan or oh, The Yukon.

So its possible that in his youth Erik Buell had some form of foundational internal combustion experience with a snowmobile, but its a longshot.

 

***

 

So why the hell am I so hung up on snowmobiles, you ask?

Can’t tell you how glad I am you asked that narrative-advancing question.

I’ve continue to have frequent SMS and cell phone conversations with offspring Finn on the subject of his Buell Blast.

Lately he related to me that the bike ran poorly once it was warmed up, which is a behavior that likely links to the performance of one of that motorcycle’s electromechanical oddities, the ‘autochoke’.

Remember that the bike’s design purpose was to be a training motorcycle, and that anything which could be done to make the bike fool- or in this case rookie-motorcyclist-proof should be and was, if possible, done.

One of those things was the ‘autochoke’.

The theory was that when cold, the enrichener circuit defaulted to open — allowing extra fuel into the intake stream. As the engine warmed, an electrical current was applied to a wax inside the body of the ‘autochoke’. As the wax heated and melted, the piston and needle would move up into the carb body and close the enrichment port, and the carburetor would then run through its normal pilot and high speed circuits.

Hot wax? What cockamamie designer came up with this Rube Goldebergian method? For what application? What ever happened to solenoids or switches? What could possible go wrong with such a strangely non-determanistic and complex mechanism?

Other than everything.

When I’d been having The Blast inspected for Maryland registration, I remember talking to the Inspector at Harley Davidson of Frederick as he went through the bike .

He had been fairly unrestrained in expressing how unusual it was for one of these motorcycles to come into his shop completely unmolested and functional.

“Man, everything is here and everything works. Brakes are good — shock and fork are good. Heck, even the ‘autochoke’ works. That never happens.”

I remember thinking to myself that this piece of data was going to be important at some time later.

If those things ‘never’ worked, it was only a matter of short time before this one joined them.

 

***

 

It was, apparently, that time.

After what is now apparently a lifetime of working on complex systems, I have developed a couple of foundational principles.

One of them is never to use a complex solution where a simple one is available.

And easy operation aside, a cable that works has got to be better than a rube-golderbergian gizmo that sometimes works and othertimes, well…

So I couldn’t be the first person down this road, and certainly not the first to fix it.

 

***

 

My first thought which is normally my best one, wasn’t here.

The first thought was that somewhere in the Harley Davidson parts catalog were parts that could be repurposed to do this simple thing.

You know — “Find the cable and mount from a Sportster, and see if they can be made to fit.”

The Blast’s ‘Autochoke’ Carb had been built around the thing — it used a different body, and the orifice in the side of the body where the autochoke sat was the size of a US 5 cent piece.

The Sportster cable and linkage would not work.

Well, the problem could be solved with HD parts — Just take the whole carb from a Sportster, swap that in there, and Bob’s Yer Uncle.

Seemed like an excessive solution.

If I was going to toss the whole carb, we’d be looking at a Mikuni Flatslide, but, well, money.

So with that idea shot, I suspected that at least one of my Fellow Blast Enthusiasts had surely figured it out.

Maybe a few decades on the Internet BMW Riders List has spoiled me to expect that the community has completely figured out absolutely everything before I even knew it was wrong, but the BMW guys and Blast folk are not operating on the same plane.

The Blast folk did have a suggested fix, but the solution wasn’t pretty.

The Blast Forum solution involved massive Dremel MotoTool destruction of the existing plastic electromechanical abomination, and getting a cable to move the large diameter slide that had formerly been moved or not moved by the expanding wax. It looked unreliable, not strong, and like something that — were it to break when you were out on the road somewhere — would leave you worse off than you’d been before, with no way to recreate the fix.

I didn’t like what I was seeing — it didn’t look like any of the Blast Enthusiasts — and there ARE Blast Enthusiasts – had actually come up with an elegant solution.

It was ON, now.

 

***

 

It was time to put on the race face, and do some top speed runs on the Google Machine.

First gear had me searching on manual choke conversion kits.

Second gear had me finding a lot of such kits being sold by motor scooter shops in convenient places like Liverpool and Stuttgart. These shops show pictures of the kits, but no application or installation data.

Third gear showed these kits were for the seemingly two most common scooter carburetors — a series of DelOrtos, and a Keihin CV.

The Blast has a Keihin Constant Velocity carb.

Fourth gear had me looking for Keihin CV Manual Choke Conversion Kits. There was a big cluster of hits on ArcticChat.com. ArcticChat, fortunately, is not a service for lonely singles above the Artic Circle, but rather, the enthusiast forum for owners of Arctic Cat snowmobiles.

Top gear on Arctic Chat showed me pictures of one of their Keihin carbs and its ‘Autochoke’. There was a picture of a replacement autochoke. Chubby rounded bit of ivory plastic… It looked familiar. As the revs climbed towards redline, an image search on their autochoke led me back… to the Blast forum.

<Sound of Very Large Relay Closing>

Where, I had kept asking myself, had Erik Buell or one of his design minions come up with the idea for this ridiculous non-simplification of engine starting technology?

Snowmobile parts.

Freaking. Snowmobile. Parts.

The Arctic Cat dudes and dudettes had similarly described sled motors that started well when cold, but ran like crap when warmed up. The autochoke seemed to have too many failure modes — whether though failure of the wax/heat mechanism, or wear that caused the plastic plunger to bind — that rendered the system dull, lifeless and inert in much less time than it took the rest of the machine to fail.

They had adopted a conversion kit made by an outfit called HOCA Racing.

You can obtain one of those kits from our good friends at Amazon.com.

 

***

 

After the UPS man left, I found myself examining the Hoca Choke Conversion Kit.

wp_20161102_14_49_50_pro

It’s really a very elegant, very robust, and completely mechanical solution.

The kit contains a machined steel plug the same diameter as the autochoke’s body. The plug has a groove with a meaty o-ring seal, and a machined shoulder that seals to the carburetor body. The next kit part is a machined retaining bracket that engages the plug’s shoulder and its drilled to accept a small screw that engages that retaining hole used for the standard autochoke. The steel plug is threaded to accept a cable sleeve, complete with slack adjusters and locknuts. Finally, the kit includes a replacement for the carb plunger that activates the enrichener jet, a spring and a cable, complete with knob and retaining hardware.

With a few minutes of tank removal, some screw spinning, and one new 5/8 hole in a side cover, The Blast will be much better off.

The members of the Blast board have helped me to learn a great deal about the operation of this not quite simple enough little motorcycle. I’m looking forward to writing up the parts sources and being an information source for them rather than an information consumer, for once.

Now I need to figure out whether this is going to be another toolkit-packing roadtrip to College Park, or whether the Blast itself will get to take another little roadtrip back to Shamieh’s Shop.

While we’re in there we’ll prolly pull and clean out the pilot jet, as well as clean the OEM air filter. Hopefully this will be enough to get the little feller running crisply, and will keep me from having to consider replacing everything intake with a Dan’s Performance Intake Kit.

blast-intake-kit

Another one of those foundational principles we’d been talking about is that stock equipment is almost always best.

Well, except for chokes, anyway.

I’m not ever going to argue that I’m a better tuner than the guy at that factory that had prototyping equipment, exhaust gas analyzers and a dyno. I’ve seen lots of examples where ‘performance parts’ reduce performance.

Both the intake tract and the stock exhaust on the Blast’s engine appear to be highly engineered. I’m kind of fond of the typical underframe Buell exhaust, too — it does a good job of keeping the big cylinder’s more obnoxious bark under control, while still letting the rider hear the low exhaust tones.

My gut tells me that modifying either the intake or exhaust on this bike will result in less drivability — flat spots, poor throttle response. Might be able to re-jet your way out of it, might not. Worst case is that you end up with an obnoxiously loud bike that only runs great WFO — a thing, it should be noted, is a tad incompatible with operation in a modern urban environment.

You might be able to ride the bike that way for a while in the city, just not for very long.

Nevermind, that being inexplicably Scots at heart, I’m having a hard time contemplating spending $250 to upgrade a $900 motorcycle.

So we’ll see if we can get what’s there working perfectly and predictably.

Finn’s Blast was supposed to be a transportation appliance, not a lifestyle.

Not that that’s ever worked before.

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One thought on “Snowmobile Parts

  1. Pingback: Venting | Rolling Physics Problem

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