• Husqvarna Motorcycles Made In Sweden - About 1988 and older

  • Hi everyone,

    As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.

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Answer Roost Boost???

Bigbill

Bigbill

Husqvarna
Pro Class
Has anyone ever tried the answer roost boost on a husqvarna Swedish bike?
The roost boost increases the rpm and supplies a hotter spark in the higher rpm range.

Now we tried it on a built 85 Honda 125cr. I ported it and added the roost boost. Since I advanced the port timing I advanced the ignition timing a tad too. This 125 was quicker than the newer 250's. We never had a 125 with the hit this one had.

Now I'm wondering if anyone has tried it on your old husky?

I'm not sure if some of the original ignitions on the husky could handle it.

Does the newer replacement ignitions they offer today have a hotter spark at the higher rpm range?
 
i have heard the motoplat is good at pumping hotter spark as the rpms increase. not as good at low rpms for starting as a modern replacement. i personally wouldnt use a roost boost. sounds like it would burn a hole in your piston. i set the timing to what it likes and it good to go. but im not sure what a roost boost actually does
 
Roost Boost keeps the electrical out put of the ignition coil up. They say it increases the rpm by 1,000 rpm.

I believe making one change is like putting a four barrel carb on a car with nothing else.
We advanced the port timing, made the ports wider for more flow, advanced the timing. Cleaned up the transfer ports, opened up the transfer ports, matched the cylinder base to the case. The hotter spark from the roost boost seemed to work with all the rest of the work we did. Two stroke engine response is all about the flow. How fast can the exhaust get out so it actually draws in the new fuel behind it. To me flow = chee.
 
I know in theory it should help.
But like adding a MSD 6AL to a good working ignition on a V8, and doing before install and after dyno testing.
Zero gains, even after playing with gap and so on.
I had it on my bike and rode it for a while and then took it off and felt no loss.
Sometimes the best way to feel a gain is to take it away and see if it feels slower to the butt dyno.
 
If I remember correctly-they only lasted so long before they quit. How electrical thing wore out is beyond me. A gimmick at the time along with roost bottles on the intake. I tried one on my Yamaha-made no difference.
 
Back then the ignition lacked the high end wattage. Today the ignition are way better on the high end. The older bikes lost the wattage as the rpm went up. On the net it was dunno tested and it added another 1,000 RPM. It boosts the wattage out put of the coil.It's like adding a hotter coil in your higher rpm engine. Let's say as an example just saying not a fact the coil puts out 8,000 watts at an idle. As the rpm goes up to 8,000+rpm the wattage may drop to 4,000 watts or less. Now bump the wattage up to 10,000 watts at idle and at 8,000 rpm the wattage may drop to 6,000watts. The stronger wattage at the higher rpm raises the rpm.I know it worked on our 125.
 
Roost Boost was a scam, it did noting but take money out of your wallet.

In relation to a Motoplat, they increase spark energy as they increase in RPM, where a Japanese ignition has very high energy at low RPM and tapers off as RPM increases.
 
The roost boost does not give an advantage to a Motoplat because Motoplat ignitions don't use a box to control timing advance or retarding. Honda's do, and most of the Japanese companies do. There is a little diode in the roost boost that tricks the timing box to keep the advance going an extra 1000 RPM.
We took one apart in the mid 80's to see what was in it. It was a diode that you could get at Radio Shack for about $1.50( yes, one dollar and 50 cents)
I tried the roost boost on a Maico with no change in the way it ran. A waste of $50. But on my Honda CR500, there was a noticeable difference, especially on top end over rev.
 
We had a gadget sold around the shows over here in Aus that went in the coil lead on your car.
It boosted the spark and cost $50.
It DID boost the spark too but when pulled to bits it was just a GAP.
If you force a spark to jump a gap before the plug it increases in voltage.
Old trick on electric fences is to almost shut the switches [ small gap ] which makes for a bigger voltage on the meter at the end of the line.

Lot of money for an air gap.
 
I just figured I'd ask you husky guys about it. I knew it worked on our Honda. I found one for a husky but I'm Leary of the SEM we have enough problems with them without adding a roost boost on it. The huskys don't need it anyway. Thanks for sharing your experience with this.

With my drag race engine I installed a 10k volt coil. This way the high rpms had plenty of power. Life before electronic ignition.
 
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