Jetting or Iceing ?

jacmmaxwell · Jan 12, 2019

My 300 ( '14 te300 , same bike as an XCW KTM ) rips for a bit in the deep then loads up and will grind to a stop. Gotta let it sit before I get it to run again, seems like its loaded up.

It gets overly warm on the trail ( new to snowbikes so not sure how normal this is ) likes to run 200+ degrees.

I'm running a snorkel type intake, I don't think its the intake design unless the added air flow has me running lean.

Jetting now:
AS 1 turn out
Needle tried 1 2 4 seems to not help ( seemed best at 4 )
170mj

Summer
AS 2 turns needle 1 (top)
162mj

Now being so new to the snowbike is this icing causing the bike to choke out and quit on me? I have a loop of copper pipe around the inlet of the carb T-d off the temp sensor fitting right at the head.... not as good of contact as a carb heater but puts out heat. The carb is also diapered in the material used for engine blankets to help keep the snow off and the heat in.

wwillf01 · Jan 12, 2019

Warm on the trail is normal but for me when my carb or slide is freezing it will act like it is rich and die out...also if you are ingesting a lot of snow it could do that... I clamp my dry filter to keep as much powder getting by the elastic ..

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eric82930 · Jan 12, 2019

What is your altitude? The main seems pretty rich. At 7000 feet stock 300s flat blubber out at wot with a 160. We run 155s unless it has a high comp head. It might just be too rich. If it does run better after letting it sit that is a sign that you froze up. Wrapibg the carb and the head together will help use some of the engine heat to warm the carb.

jacmmaxwell · Jan 13, 2019

7,000 at 20 degrees puts me a bit rich on the main by the book.

I run a 162 summer from 5 to 9500 without issue but I don't spend much time in the main during the summer.

Your running 155 in winter and at what elevation ?

Misha Subo · Jan 13, 2019

jacmmaxwell said:
My 300 ( '14 te300 , same bike as an XCW KTM ) rips for a bit in the deep then loads up and will grind to a stop. Gotta let it sit before I get it to run again, seems like its loaded up. .... not as good of contact as a crab heater but puts out heat. The carb is also diapered in the material used for engine blankets to help keep the snow off and the heat in.

Stop putting diapers and crabs in your carb and the icing will disappear right away!:face-icon-small-win

jacmmaxwell · Jan 14, 2019

Shook out the crabs ( and corrected my spelling ) ... starting to think the icing is from the prefilter letting moist air in. I didn't seem to have this issue with the stock filter , but it was plugging up pretty bad.

The diaper , cover , jacket ... over the carb was an attempt to keep heat in and snow off the body of the carb but it seemed to have zero effect on the problem.

I'm going to go back to stock filter and see what happens. If it works out I may just get a prefilter for the stock setup and run without the side panel to make cleanouts easy... or get a uni pod filter to run under the prefilter.

Ben 500RR-S · Jan 14, 2019

Just last month, when we finally got the KTM 300 on the snow, the carb was icing up all night long. We'd ride around and after about 10-15 minutes the engine would just quit.

We'd wait about 5-10 minutes and the bike would start up and run fine again for another 10-15 minutes until the carb iced again.

We tried the bike on another day and same thing.

Now with a brand new Smartcarb, a PST carb heater plumbed to a Thermobob along with a PST carb jacket and a Velocity Intake with a matched Outerwears filter skin, there has been NO more carb icing and the engine just runs like it should in every condition.

eric82930 · Jan 14, 2019

We ride 8 to 10k
You sound way rich everywhere. no needles that I've tried.work on clip 4 at this elevation Asuming clip 1 is top (lean).....
If your wrap is really good it can work without heat. The pre fillers just make it richer.
The xcws had the lowest comp heads and don't like much fuel. High comp 300s can take a 160 sometimes but don't Rev as well as they do with leaner main. 158 was about the richest I can get good overev.

M5- · Jan 14, 2019

If its running decent then it stops it's icing up. Carbed 2 strokes in the mountains need carb heat end of discussion.

M5

jacmmaxwell · Jan 14, 2019

I rebuilt my heater , it was just the loop wrapped around the inlet. I hammered out the collar until I got a good clean fit ( dab of gasket maker at the seam will be needed ) then soldered on the loop, it should conduct alot more heat this way.

Not as fancy as store bought but should be just as effective. Just payed tuition for my oldest so gotta get by with dyi for a while.

I'm going to keep my intake with the outerwears prefilter for now as that seems a very proven setup and the bike runs very well until it ices up... Once I get iceing figured out I will play with jetting.

eric82930 · Jan 14, 2019

That heater looks great. If it's working you should even feel some warmth in the float bowl. keep in mind for it to work the coolant must be hot and in deep pow with rich jetting 2 strokes with thermotstats won't even get hot unless they have a really good wrap.
Don't give up. The 2 strokes sing like magic oh so sweet when setup right way more fun than a 4

M5- · Jan 15, 2019

If you had a piece of header wrap you could wrap the carb throat and copper tube to help direct the heat inwards then cover the header wrap with something waterproof. If you don't have a thermostat in your cooling system you might want to add one to help get and keep the temps up. Its easier to prevent ice than it is to get rid of it once it has formed.

M5

portgrinder · Jan 15, 2019

listen to m5. he knows whats up.

get a coolant temp sensor. if it wont stay about 75F in the deep, you dont have enough heat to warm the carb and it will stick. also have a tether switch for that reason

if your temp is decent and its still icing then you arent transferring enough heat to the carb through your heater gizmo

you also need to keep the vents clear. run them up under your seat and fab up some sort of filter/breather for the end of them.

once you get that sorted, keep jetting down till you squeak it, then rebuild and jet back up one size. done deal

jacmmaxwell · Jan 15, 2019

I do have a T-stat , its 135 degree and I've yet to see less than 120 on the gauge. Long term I will ditch the stock t-stat for a thermo bob as with the stock setup I'm by passing twice , once at the t-stat ( built into it so can't block ) and a second one on my carb heater.

I didn't have any header wrap but I did make up a new carb blanket out of vinyl coated canvas to try and hold some heat in and keep the snow off the body of the carb.

I was wondering about vent lines and I will work something out with them for sure.

tek9tim · Jan 15, 2019

Nice! Looks like a proper Maxwell fix. I'm sure you'll have that bike singing before too long.

jacmmaxwell · Jan 16, 2019

LOL , yeah... But take another look at that blue fabric.

That's an old PLS lumber truck side tarp from Packwood lumber. I still have the entire Packwood Lumber / PLS log section of the tarp. Always meant to make a garage banner out of it but never did.

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Jetting or Iceing ?

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