Jetting, S3 heads, Squish band, and other fun stuff!

[memphis2857]

Ok so I have a 2011 300 with 60 hours on the ticker now. I bought the bike in January of this year with less than 10 original hours on it. Since day one I have chased my tail with jetting issues. With the stock pipe I settled at 178 main NEDW #2 and 40p. This made the bike run well but would load up pretty bad after long periods of slow riding and the when the time came it would take a bit for it to clear out and run proper on the main. Then I added the HofHP pipe and silencer. This totally wrecked my jetting and it was back to chasing proper setting. Ended up with N3CH#3 40p and 180m. This makes the bike run Just OK. Again it loads up pretty bad after long periods of slow riding and takes time to clean out and get on the main. If I take a quick rip down the road at WOT it seems pretty lean on the main and the VP110 fuel I run turns the plug a nasty lean yellow color. So with all the knowledge on this forum and my experiences my main jet seems way too rich but in actual running order it seems too lean. Also the loading up concerns me this has never been an issue on any other bike I have ever owned. Thoughts?

Now onto the S3 head. I ordered it from motocross center in Spain and had it in lees than a week. Only $200 to! Can't beat that. Anyway I did some squish measuring and with the stock head it checked in at 2.12mm. With the black insert it measures at 1.58mm that's a .54mm improvement which translates into roughly 2cc less volume giving me roughly 23.7 cc in combustion chamber volume? Using a simple calculator that puts me around 13.4 CR. sound right to you guys? So the S3 head does bump compression a bit but I am a little disappointed I didn't get a better squish band clearance.

The bike runs a lot better now. It pulls hard across the board and has a much more pronounced hit. It does sign off a bit early now due to the increase in compression. It actually cost me about 4 mph in top speed. Doesn't much matter to me because I can't ever remember needing more top speed. The jetting seems a little better now but I still fell like I could go to a 182 main. Seems so rich compared to the norm.

I guess I am a bit all over the place in my ramblings and I don't have any real questions just would like your thoughts.

Oh and the whole S3 head thing started after I switched bikes with a buddy and realized his clapped out 05 300 Katoom had twice the power of my bike! He handed my bike back to me and said it handles great but man it don't have any power! I said your bike handles like crap and is a rocket ship! At this point I decided I need more power!


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[GGRider01]

I've been contemplating measuring my squish and running my head to a machinist. Might have to do the cylinder, who knows - never done it before. You think the S3 is worth the money and saved hassle?

It could just be the camera or my mere 1 year experience jetting these 2 strokes but that plug looks a bit white to me. What altitude are you at? I'm running a 170 main and can take it anywhere from 4500 in town here to about 8000. I haven't tried taking it any higher but a quick adjustment of the screws seems to do get it right on point with no issue.

[memphis2857]

You can get better results from having your head machined. Just be careful if you cut too much to correct squish your compression goes through the roof if you don't cut the combustion chamber to gain back the lost volume. The S3 is pretty and my bike wasn't down for 2 weeks but the squish could still be better. I am going to send my stick head off and have it worked over by Ron Black.

I ride 0-1500 ft elevation


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[Rick]

Haven't rode a 300 in some time.....BUT, what I do remember is, it felt slow, and linar.......which is not a bad thing.....just because the "hit" isn't there...dosent mean it has no meat........food for thought.....I rode it differently....short shift and twist!

[Jakobi]

Covered all of this in one of my engine threads. I ended up using an S3 head with a single .5mm base gasket, the high high (black) insert, milled to correct the compression ratio. Really once you factor in the price of an S3 head and then machine work to optimize it it's not really worth it, but it does look cool!

2nd engine I had the same tuner machine the oem head. Same end result.

Ideally you want the squish under 1.3mm to take full advantage of the increase in efficiency, and also having the squish angle matched to the piston helps too.

My 300 had a stock clearance of 2.6mm - epicly huge - and was near unjettable.

Your piston and spark plugs both look quite dry.

[(F5)]

1mm is good with new angle, and equal compression back. search my thread on it or just pay someone