Blur 150 mods to increase top speed

[blurblaine]

29 OCT 2010

This may be on a old thread, but I haven't found it, so here is the 'ask'...

I'd like to increase the top-end speed on my Blur 150. I'm not trying to create a racer and don't really care if low and/or mid-performance is altered ... I just want to have 5 - 10 mph higher at the top end.

So, how can this be accomplished (besides switching the 150 for a new 220 engine)?

Thanks in advance for your answers

[babblefish]

In order to get that 5-10 mph increase, one needs to do one or both of two things: 1) increase the engines rpm range and/or 2) change the final gear ratio. Unfortunately, I don't know where to get different final gears for the Blur, so increasing the rpm range or "red line" of the engine is your only option. Using a variator that is "overdriven" such as the Dr. Pulley is another option I suppose. These "overdriven" variators have a slightly bigger diameter (115mm vs 112mm) variator plate, but unless you can find a slightly longer belt, I'm not sure the scooter can take advantage of the oversize. A more aggressive cam would help the engine breathe, though stiffer valve springs may then be neccessary. A freer flowing intake system may also help. Basically it means getting rid of the stock airbox and using a foam or K&N type filter. This will require rejetting of the carburator to make up for the increased air. The stock carb is I believe 24mm. A 28mm carb might be beneficial. Lastly, the stock cylinder head is pretty restrictive so some port work to free up the intake and exhaust flows would definitely help. When I did the port work on mine, I found the stock ports were very "congested". I ended up removing quite a bit of material to free-up the air flow. You can see some of the results in the Blur threads under "Seized my Blur's Engine". Unfortunately, I forgot to take any "before" pictures. The intake manifold should also be reworked to match the increased intake port size or an aftermarket intake with a larger opening can be used. Think of an engine as an air pump because that's all it is. If you can increase it's efficiency by allowing it to flow more air/fuel, it'll allow it to rev higher. But...don't open up the ports too much or make the carburation too big or else you'll sacrifice too much torque or low end horsepower.

[davelhunter]

I wanted the exact same thing with my Blur 150. I tried everything: 8 different sets of dr. Pulley sliders, a Dr. Pulley variator, and the NCY full transmission kit, all with minimal results. I finally realized that there was only 2 ways to get the speed increase: 1. Diferent final drive gear (which I could not find anywhere for the PGO motor - the other gy6 gear sets would not fit) or 2. Big bore kit.

[babblefish]

A big bore kit will increase your overall torque, but will increase your top speed only on hills that requires more torque than your stock engine can provide. In other words, if your engine's rpm drops off going up a hill because it ran out of torque, the big bore kit will help by allowing the engine to reach it's upper rpm range hence top speed. Remember, only changing the difference in speed between the engine rpm and rear wheel rpm will you get more top speed. Hope that made sense. As I mentioned above, this can only be done through changing the final gear ratio or increasing the engine's upper rpm range.

[gearhead]

go with a 150/70/13 tire and dremel/grind off some of that metal off where the swing arm attaches to the case so that you can fit the wheel and you can influence the gear change that way.

[babblefish]

I was actually thinking something simular, but with a 140/60/13 tire. Hopefully the smaller size won't require any modifications. I'd also put the normal rear tire (130/60/13) on the front to balance it out. This should also make the speedodometer a bit more accurate.

[Lostmycage]

I was actually thinking something simular, but with a 140/60/13 tire. Hopefully the smaller size won't require any modifications. I'd also put the normal rear tire (130/60/13) on the front to balance it out. This should also make the speedodometer a bit more accurate.

For some reason it seems that this has been tried before with success. That's completely and totally only from my questionable memory (in other words, I'm not going to search for it, but I'm 95% sure there's a post or two about it). I know for a while, Scooterworks actually recommended a 130 front tire.

[KS Power Nick]

There is also a 140/70-13 tire through some brands. That would give more top speed with out going to the super fat 150 tire

[BlueMark]

Add a windshield.

[killbilly]

Add a windshield.

I've heard several people offer this.

My question is: Why does this work? It would seem to me that it causes more drag and wind resistance. Is it that it cuts down on pressure drag or what?

[Lostmycage]

Add a windshield.

I've heard several people offer this.

My question is: Why does this work? It would seem to me that it causes more drag and wind resistance. Is it that it cuts down on pressure drag or what?

It causes less wind resistance. Which is more aerodynamic, a torso with arms and clothing acting as sails or a rigid smooth surface that cuts through the wind?

There's diminishing returns after you get to a certain size, but that's usually on full fairing bikes with barn door sized windshields.

[Mikie M.]

A set of DP sliders, about a gram lighter than stock, will get you a couple of miles per hour on the big end. An added bonus, of course, is slightly better take-off and accelleration.

A quick edit here. Stock weight sliders would probably provide the best gain in speed. Sliders, by their design, tend to move the belt a little bit higher up the variator pully face, thereby increasing top speed.
Sliders are hands down, the best bang for your buck.

A clarification here. Higher up the variator drive face would translate to a lower numerical ratio, if a numerical ratio were assigned to it.