Pilot Jet Mixture: 2013 300 Factory

[ken_hosking]

I have recently taken delivery of a 2013 Beta 300 factory, and in almost every respect it is a superb machine. However, the throttle response from low rpm feels a little rough, as if the pilot jet mixture is over rich. Tweaking the pilot jet screw has had only minimal effect. Has anybody else experienced this issue, and possibly tried a smaller pilot jet, or found a different solution?

[nzralphy]

Everyone asleep mate, when the sun comes up you'll get an answer.

[beta7492]

I have had this same problem, struggled with it trying to get the air mixture right but no luck. Iv raised the needle now so the clip is on the lowest slot and its a bit better but not perfect....

[0007]

That's a different problem

ken says his pilot is too rich, you made your transition circuit richer

My 010 feels lean on the pilot, my Rev was the same

The air screw really only cleans up idle and just a hair open throttle, after that there is almost no effect

Pilot is partial throttle to about 1/3 after that it flows constantly so it can slightly richen all circuits but minimal effect

Then needle and then main above 3/4

[peterh]

Hi,

I have used the following process successfully with my Beta Evo's having also installed Boyesen Reeds. I found this process easy to work with rather than doing the throttle chop method (in surburbia).

http://www.smellofde...ydy/jetting.htm

Note that the guide starts with the needle clip in the middle position and changes are then made around that starting position. So getting the pilot and needle correct without any influence from the main jet (or making me understand when the main jet circuit was coming into play) worked well for me.

Good luck.

[lineaway]

Thanks Peter! That`s the most logical guide I think I`ve seen. People usually just try the main and clip on the needle. Last ten years I`ve started with the pilot.

[0007]

I presume that system is designed for an automatic transmission scooter

Full throttle in neutral?, full throttle on a stand in 6th gear?

Full throttle in 6th gear on a road with load will give you a different plug color

I would not rely on jetting a manual transmission bike with no load like that

[dan williams]

Thought the same of my '13. Went one leaner on the pilot and didn't like it at all. Went back to stock and dropped the needle 1 groove. Helped immensely. I know it shouldn't off idle but it did. Also put in VForce reeds. (luv 'em) and went down one size on the countershaft to make 2nd my main gear.

[ken_hosking]

Many thanks to all who have responded to my post.

Your post is particularly interesting Dan, as I have had the same experience with the smaller pilot jet and I am about to change it back to standard. I will try the needle position alteration at the same time.

I have also altered the gearing to make second more useable, in my case by going from a 42t rear sprocket to 44t. I thought that going from 10t to 9t on the countershaft might be too big a change. I would like to know your experience with your gearing alteration.

[dan williams]

I did the same gearing change on my '05 and '08 Rev3s. I just found them a bit to abrupt with the stock gearing and I'm a plonker anyway. Speed through the section has never been my thing. With stock gearing I just found 1st to be too slow and second just a bit too fast on the 270 and it seems the same for me on the 300. I ride most things in second now but 1st is still there when I need a crawler gear and there doesn't seem to be that much of a difference from stock and third is useable in more situations. I also haven't noticed any appreciable difference in chain wear.

[ken_hosking]

I did the same gearing change on my '05 and '08 Rev3s. I just found them a bit to abrupt with the stock gearing and I'm a plonker anyway. Speed through the section has never been my thing. With stock gearing I just found 1st to be too slow and second just a bit too fast on the 270 and it seems the same for me on the 300. I ride most things in second now but 1st is still there when I need a crawler gear and there doesn't seem to be that much of a difference from stock and third is useable in more situations. I also haven't noticed any appreciable difference in chain wear.

Thanks for the feedback Dan. After riding for two days over the weekend my impressions of the lower gearing are that, even though I have reduced the final drive ratio by less that you have done, I seem to have a similar effect. I find that using second gear is easier than before, especially where a tight turn precedes a step or a climb, and third works well also.

As for the mixture, re-fitting the stock pilot jet and dropping the needle one notch made the bike feel much more responsive. Unfortunately, the engine suffers from detonation when hot, but not under load, rather when the throttle is rolled off rapidly. At first I suspected that the noise was mechanical in origin, but an experienced mechanic who rode the bike felt certain that it was detonation. I changed the plug, making certain that the gap was correct, tweaked the pilot air bleed screw but to no avail. I remember that I had the problem prior to lowering the needle, but after fitting the smaller pilot jet. It has been suggested to me that the engine could have a carbon build up, but with only 30 or so hours since new I rather doubt that would be the case. I am using ethanol-free 98 octane fuel with a 1.5% oil/fuel ratio using Motorex oil. Any suggestions would be welcome.

[0007]

Try a Yamaha marine dealer for a product called "Ring Free"

Incredible how it decarbons a motor, if you still detonate

Then it was not carbon buildup

My Evo will detonate at mid to high rpm with small throttle opening

I think this is TMDT

(These machines do that)

[dan williams]

The best way I've found to deal with the ping is 110 Octane VP C-12 race gas. Just the nature of the beast with a high compression engine. You could try a thicker base gasket but you'll lose some pop out of the throttle.

[ken_hosking]

I am able to report some success after tinkering with the carburettor. It seems that the pilot mixture was too lean, not too rich, as after fitting a size 50 pilot jet, the response was much improved. I then tried a size 4 slide (OEM was 3.5) and lifted the needle to the top notch. The engine runs very sweetly now and detonation has all but disappeared.

In relation to Dan William's last post, Motorcycling Australia does not permit the use of leaded fuel or fuel with greater than 100 octane rating in MA controlled events, so that changing the fuel is not an option for me.

Since making these changes, and experiencing better engine responsiveness, I find that I seldom use first gear now.

[dan williams]

Lesson noted.