carls 910 seems thermostate??

BILTIT said:

From what i have found they offered a 55cc and a 50cc.

I spoke with jack at carls and he said they were 12:1 and 13:1 compression for those heads, not the 14.5/15.5 that seems to be floating around.

I run the 50cc heads, or hope to if my pipes ever show up.

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I said my heads were 15.5 and 14 respectively. I never said they were stock as offered by carls.

Oh Ic, I didn't realize you aren't running Carl heads. I am just trying to keep the info clear for the next person looking, not alot of info to be found for these motors on the net.

BILTIT said:

Oh Ic, I didn't realize you aren't running Carl heads. I am just trying to keep the info clear for the next person looking, not alot of info to be found for these motors on the net.

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Im running carls domes but the set thats in the sled is cut to make the compression 15.5/1. I have the 15.5 domes 14/1 domes 50cc and 55cc domes now.

To my knowledge carls offered 47cc 50cc and 55cc domes for this engine but made several other varying compression level domes for this engine back in its time.

You right there is not a lot of info. Mine only runs the way it does because I patched together the little bit of info I actually got from Carls, the info I got from a couple people here and made some educated guesses as to how this sled should be tuned. I got ballbark this year for flatland and right on the money for elevation.

What I know based I how my engine runs is it likes 8300-8350 RPM's. The previous owner told me 8200 but I put an actual know calibrated tach on it and it wasnt clutched to hit 8200 anyway.

This engine seems to be more based on torque than over all HP. It makes good HP but the torque is what is the most impressive part about it. I can litterally fully let off the throttle going up a climb, stab it again and tractor right on up.

I can climb things now with zero run that I had to get a sizeable run at before, makes riding in the trees really fun. Another thing about this engine is that it loves fresh air. The more you can get to it the better. I think I will be going to a mesh hood to ensure that I dont heat soak. When riding in the tight trees a couple of times with the hood on my pipes heat soaked and it took a while for the sled to come back.

I forgot to mention I run the XCR style remote thermostat with scratchers, highest i;ve had my temps get is 135.

Some good info there. So far with my 910 being low on compression it will only pull the similar setup as my 800, it has more torque though.

Next year i will put in a fresh top end and see how it goes.

I will also be adding as much fresh air as possible.

With just a restrictor in mine it will run 80-100 in the snow, i have seen up to 140 on trail with minimal snow and warm ambient, no scratchers.

I run an atacc on mine although I haven't got it dialed in yet. The previous owner ran the older version (variflow) on it.

I dont run tempaflow or veriflow. Im considering running bored carbs here soon. Maybe lectrons. See if we cant make some more power here. :face-icon-small-hap

Mine has bored carbs, 40mm. Or are you talking bigger yet?

Just a heads up for any purchasing pistons for a 910 in the future. I bought mine from carls and they showed up in a crankshop box so i went the crankshop website and they have them there for $50/piston cheaper than carls sells them.

http://thecrankshopvt.com/product_info.php?cPath=21_23&products_id=404

BILTIT said:

Mine has bored carbs, 40mm. Or are you talking bigger yet?

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With this motor amf bored 40s keep an eye on the car slide on the air box side the corners like to break off .it does not happen to all of them but I have seen it more than once. Also if the skirt has been broke off the cylinder ( real common for this motor) it may never hold up ever again how you tell is there will be a number on the back side base of the cylinder call millennium and ask the history of it. Just some things to watch for

Good info, thanks!

sled_guy said:

What mixture of av or race gas are you running?

Lean in and of itself won't cause detonation although richening can mask detonation (Yeah, that sounds weird). I've seen DET sensors pick up things like exhaust springs vibrating and such.

Easy test is to up your av gas mixture and see if the DET goes away. If it doesn't then you can start looking at things like exhaust springs and such that might be setting off the DET (just squirt a line of silicon on them to stop their vibration).

sled_guy

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Thats because they really only read vibration (engine knock). Many things can contribute to false readings.