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Messages - KTRacer14

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1
KTRacer14 good info. what kind of a SC2 setup do you have? A friend of mine has a 38 installed (not a sherco, an other popular brand). He is kinda happy, but commented that he should have bought a 36.
I am considering of getting one but the price is an important factor.
cheers, erdat

erdat,

I went with the Mfgs (Technology Elevated) recommendation.  For the Sherco 300 2T, that is 36mm.  I think they also recommend 36mm for other 250-300cc 2Ts. 

So far it runs great.  I am about 12 clicks leaner than the baseline they set the carb at.  I would say that initial throttle response is about 90% as good as a well jetted carb set up.  It is good...but not quite perfect.  Throttle feel/control (holding traction, lugging, etc) feels better than a std carb.  Mid to top end power feels the same.  Fuel mileage is noticeably better.  500'-5,500' elevation....no change in how it runs, which was the whole reason I decided to go with the SC.  That to me is worth a lot.  Spooge is reduced to about 20% of what it was with a carb.

One thing I have found is the bike idle RPM changes quite a bit as the bike warms and get hot.  If the idle is perfect 5 minutes into a ride...it will be 300 RPM higher 10 minutes later.

Another weird nuance is if you lay the bike down to the left, when you get the bike back up and re-start...it is really rich and takes a bit to get it cleaned out again.

It was quite a bit of work modifying the air boot to fit for proper installation.  I did a lot of careful grinding to get the shape right, and allow for the compensation port to be properly exposed.  They have a good video showing how to do this.

So far, I give the SC2 a 9/10 rating. 

2
How much taller was the stack?

Keep us informed on the results.  Sometimes with situations like this, it turns out that you were the first one to actually USE the product, and sometimes there are some teething pains that need to be worked out.  A good company will work it out, and that is how they dial in their products. 

3
I think some of you are very confused at to what 1/8 throttle is, and where the pilot circuit is active.  The pilot circuit is active everywhere.  That is why you adjust it first.  Other circuits simply overwhelm its effect with increased throttle opening.  The needle taper starts to be active at about 1/8 throttle.  Go see how much throttle adjustment it takes to bump the idle RPM by 500.  It is tiny tiny fraction of 1/8 throttle.  Adjusting the idle up by 500 is going to come nowhere close to using up 1/8 throttle.

FYI...I got tired of re-jetting for Alt changes so I took off the Keihin and put on a SmartCarb SC2.  Problem solved.   

4
Recommended idle RPM per the manual is 2200 +/- 100.

Per my prior post.... prior testing was at:
4500 feet elevation
50 Def F
30% humidity

But the last few times I rode were at:
500 feet elevation
70 Def F
20% humidity

Probably similar air density.

I finally played with the float bowl.  It was at 7.4mm (mounted carb on a adjustable angle plate, and used a pop-off gage on the fuel line to get accurate readings).  That is right on the setting most have found to work.  But it clearly is NOT working right....so I raised it about 1mm...to 8.6.

I ran it and bike sounded a little less rich at idle, but it is still not acting right.

38 pilot.  Set AS at 2 turns out.  Set idle RPM at 2200 after warming bike up.  Then play with air screw:
1 Turn Out: 1800 RPM Idle
2 Turn Out: 2200 RPM Idle
3 Turn Out: 2500 RPM Idle
4 Turn Out: 2450 RPM Idle
5 Turn Out: 2480 RPM Idle

This is at least an improvement.  Before, the RPM kept on rising and rising.  The more I turned out the Air Screw, the higher the RPM went.  At least it stopped doing that!  Every carb is different.  Maybe this carb just wants a smaller pilot jet....  I guess I need to get a 35 pilot jet...  Really aggravating though...that the Sherco manual is so far off.  I mean it is not even in the right zip code....  What is the point of publishing recommendations that are so far off.

5
erdat,

Thanks.  I reviewed that, and the initial adjustments from your link are exactly the same as my method. It says to start with the idle system (pilot). 

Quote
You will find a screw position that gives maximum engine idle speed such that turning the screws either in or out from that position causes engine rpm to decrease. This is the correct position. Think of it this way: The ideal air-fuel mixture makes the most horsepower at a given throttle setting—even at idle.

This is the problem, as I have already noted.  I am down to a 38 pilot, and no matter what I do...the more I turn out the air screw, the more idle rpm rises.  I get to 5+ turns out...and the idle just keeps going up.  So as it relates to my issue, your procedure is the same, and gives the same result.

I will play with the float bowl and see what I can figure out....

As for reading RPM...I installed an hour meter that has an RPM setting measurement mode.  I use that.  I also have a variety of electronic test equipment, including logic analyzers and oscilloscopes.  It does not take much circuitry (some wire wound around the spark plug wire, some filters and Schmidt triggers) to  create a square wave to measure RPM.

6
General Discussion / Re: Frame problems
« on: April 11, 2021, 09:37:08 PM »
I have no idea what Sherco guys you talked to. What I know for sure is that the bikes that run the world championship and their respective practice bikes use standard frames without any additional reinforcement...and these are very stressed frames that are regullary abused on mx tracks, certainly more than ours. I do not see and do not know any contraindications to the use of sherco in mx track

MattHorse300... took me a while to find the reference.  Here is what I was referring to. 

Quote
The engineers at Sherco once told us the reason they don’t offer a motocross bike is because the current frame is designed to be more compliant and that big MX jumps require a more rigid design. We understand completely. The Sherco has a comfortable feel on the trail that’s hard to attain with a motocross bike.

https://dirtbikemagazine.com/sherco-250sef-full-test-2/

"...BIG MX JUMPS REQUIRE A MORE RIGID DESIGN.."  I guess that statement is subject to interpretation, but the way I read it, they are saying big jumps require something different than what they build.  It thus does not seem like a mis-statement to say the frame is not suitable for big jumps (hard MX riding).

As for the MX sections of championship Enduro races, are they really that hard of hits?  The Euro style MX tracks seem to have a lot of big singles...and mild (faces not that steep) high speed jumps.  Sending a single to flat is not the same as casing a big gap into a steep face.  Are they jumping gap doubles and triples into steep faces if you make a mistake?  I mean a few years back I cased a triple (like an idiot, I was not paying attention to the water truck...greasy jump face) on a YZ250F.  I broke the right stock Ti footpeg!  Blew through the suspension front and rear, and damaged the shock.  It had to go to Enzo to get repaired.  Oh yeah...I also exploded my right wrist.  The medical term is comminuted intraarticular fracture of distal radius.  I did not crash.  I rode it out.  Thank god I had the foresight to move both my feet forward to the heel stops on the pegs before I hit...or I probably would have broken legs/ankles.   

The thing about an Enduro bike is the suspension/valving is so much softer...so if you do case hard...the frame is actually going to take an even HARDER hit than an MX bike because the suspension will not absorb / spread out the impact impulse.  It will just blow through and bottom.  If took that same hit on an Enduro bike...I probably wold not be riding today as both my lower legs/ankles would have been broken when the suspension blew though even faster.  Of course...maybe it would have snapped the frame too.... 

7
General Discussion / Grinding Stone Hard Enduro
« on: April 08, 2021, 12:20:41 AM »
Lots of Sherco's in the mix! 

I bet there were a bunch of parts orders placed after this one....

https://www.youtube.com/watch?v=fPBlvFUv8MY

https://www.youtube.com/watch?v=x1IM0oANlWs

Anyone going to give it a go next year?  I am thinking about it....



8
General Discussion / Re: Frame problems
« on: April 08, 2021, 12:17:53 AM »
I have seen Sherco staff comment specifically that they do not make a MX bike because the frame needs to be so different to withstand the hits.  This implies to me that these Enduro bikes are really not suites to an MX track....

9
Sfade,

Were you able to measure the disc stack ups yet? 

If you get the stack heights correct to match stock you may be surprised how much different the Rekluse stack behaves.

10
Take the stock stack of friction discs and metal plates and measure them with calipers.

Take the Rekluse stack of friction discs and metal plates and measure them with calipers.

You are going to find that the Rekluse stack is thicker.  This is the cause of the problem. 

Rekluse should be able remedy this issue with some thinner metal disks.  That should resolve the issue. 

11
I think you must be right about the float bowl, because what I am seeing makes no sense at all.  I have always been told that jetting a PWK must be done in order:

1.  Pilot + Air Screw
2. Needle
3.  Main

You have to get the pilot right first before you can do anything else.

To tune the pilot, do the following:
1.  Put in your best guess as to which pilot is correct
2.  Warm the bike up.
3.  Set the Air Screw at 2
4.  Adjust the idle so the motor idles about 500 RPM higher than recommended.  So for a Sherco 300, set the idle to 2600 RPM.

Now play with the air screw.  You want to find the setting that produces the highest idle RPM.  If that occurs between 1 and 3 turns out on the air screw, you have the right pilot.  If below 1, your pilot is too lean (small).  If highest RPM occurs with the air screw more than 3 out, your pilot is too rich - go smaller.  Once you have the right pilot, you can tun the air screw for feel.  Usually it runs best about 1/2 to 3/4 richer than the "high RPM" setting.

I went though this, and got no good results.  The response to air screw tuning is not right.
4500 feet elevation
50 Def F
30% humidity

Started with 40 pilot. 
Warmed bike
Set RPM to 2600
Played with air screw.
Could not find a max RPM.  The more I leaned it out (air screw out more) the higher the RPM got.  RPM never peaked...all the way to 5 turns out....it just kept going up and and up.

So changed the pilot to a 38.  Same thing. No matter what I did...the air screw setting never gets "too lean".  The more I turn it out...the higher the RPM goes.  Also...even with a 38 pilot....the air screw has to be at least 1 out...or the bike will die. 

Must be a screwed up float bowl? Right?

12
Lv2 - Yes....the bike came with the strange jetting set up...that is completely out of synch with the rest of settings on the chart.

40 Pilot
N8RE Needle
165 main

Look closely at the chart...there are actually only 10 different settings.  If you go diagonal down and right, the settings duplicate on the diagonal...except for the 25-36 Deg at 300-750m setting...which is just out of whack.

alang,

What temperature and altitude do you run that set up for?


13
2021 300SE Factory:  In general, how far off is the jetting chart in the manual...?   I set the bike up per the manual, and it seems very rich at 1/4 to 1/2 throttle.  As soon as you open the throttle, it starts 4-cycling.  Really absurd how rich the chart is.  It seems almost useless.  Just riding around my property, the plug looks too rich to go for a real ride.  I am afraid I will foul plugs right and left....

  • From what I can tell, the pilot jet needs to be about 1 leaner than the manual says.  So if it says run a 42...run a 40. 

  • Way too rich at mid throttle.  I will probably have to jump to what...a N8RG as I will run out of clip positions.  Two needle letters is equivalent to 1 clip position...right?

  • The main recommended does not seem terribly far off....maybe go one leaner. 

Is this at all consistent with what others have found?

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