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Ever heard of a 2 stroke with no reed valves?


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A friend of mine has this polaris explorer(96) he aquired. This thing won't start for longer than a couple seconds and thats with a heavy dose of starting fluid. Crazy setup, chain driven four wheel drive with a big air cooled single cylinder 2 stroke. It's got about 95lbs of compression with new rings, bore and piston. We've cleaned the carb really good. I was thinking about what it could be and noticed this thing doesn't have a reed valve. The guy he got it from didn't give him one so??? I'm gonna check the exhaust for restriction next. It was a mobile home for dirt dobbers when he got it.

Edited by Rustbag
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Believe it or not there are many 2 stroke motors out there without reed valves. I'm not quite sure how they work but I have seen a few of them. For example, check your weed-wacker. I'd be willing to bet it has no reed valves

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There are some 2 stroke engines that don't use reed valves... the Rotax 670 for example has a rotary valve mechanisim instead. Also Detroit Diesel engines are 2 strokes with no reed valves, but they use exhaust valves like a 4 stroke. Those are just 2 off the top of my head... so there are some out there Polaris may have another...

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The sweedish vintage dirt bikes like the "Bultaco"..or however you spell it. I belive some of Yamahas early street bike stoff was the same.

I've seen it in person, but don't know how to explain it :blink:

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I have seen a polaris explorer 1994 2-stroke do the same thing and found out that the piston skirt had chipped off. It was doing exactly what you are describing. And we checked everything even the exaust for mud dobbers. The piston was even new so give that a check, should be easy to check.

 

Good luck

Edited by DreamShee03
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I couldn't find anyone who listed reeds for the 300 xplorer. seen it list some of the other polaris 300s like the scrambler or somethin. the p300 is all I found not the same.

 

Hey dreamshee, did the one u looked at have reeds?

 

stupid polaris :flush::flush::flush:

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It's probably what they call a "piston port" or "piston reed"type of engine. the old arctic cat twins had this type of set-up on their 650 and 700 snowmobile engines. some even have a small internal reed positioned between the cylinder and the case. i've got one of these cylinders kicking around here somewhere and can post pics later today.

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If I'm not mistaken the lt250r had a case reed system and the reeds were underneath the cylinder.

 

That is exactly what I was going to say. There are two common types of reed inductions.

 

Intake reeds (most common by far) and case reed.

The latter won't have the big square or round block between the carb and the cylinder, rather it will be under the bottom of the cylinder.

 

The case reed is terrible in MY OPINION for a few reasons, them being:

The whole cylinder has be removed for any type of Reed Maintenance and replacement, and

You only have one side of reeds that flow down into the crankcase.

 

We all know V Force reeds put out power efficiently because of more survace area (4 per block instead of the traditional 2)...now, cut the traditional two in half. 1 reed surface on case reeds.

 

My old 85 LT250R had this. Zuke' changed this in 87 I believe, until the last year the 2 fiddy was made. 85 and 86 are the same motor design...

 

HATED IT...

 

However, some 2 strokes don't have traditional reed cages, etc., as pointed out....

I would be surprised if Polaris took that route....but it's certainly not out of the question.

 

:D

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The polaris explorer didnt have any reeds. Check the pipe to see if it is clogged and check the skirts. Just look into or feel in the intake with your fingers, cause the exact "to a T" thing was going on with the explorer that we had in our shop.

Keep in mind this was on a 1994 so i dont know if they have changed anything but i highly doubt it.

 

Hope this helps you out

Edited by DreamShee03
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