Thanks!.. It was one of my first projects on my bench top lathe.

2000 KLX300

Ride on
Brewster

 

I haven't been a follower of Adventure Rider. Which forum is it in?

Ride on
Brewster

 

This is interesting. I run lid off and it runs great. Lid on, with or without snorkel, and the power drops dramatically (DJ needle, powerbomb, HMF slip on). I suppose rejetting with lid on and I could maybe find the right "spot." But it runs great, so why mess with it? Another member here suggests that the lid and snorkel should be on to keep intake velocities high for best performance. My feeble mind thinks that if the lid is off, fewer constrictions yields better airflow in and improved performance. Any thoughts on this? Hope it's not hijacking the thread...

 

It's in "Thumpers". Since it just started in the last few days, it seems to stay on the first page regularly. I'd just like to hear your take on it since you've done some experimentation on it.

 

For a new topic, there sure is a lot of chatter and little actual content. Let me start out by saying that my attempt at FI was a few years ago and I never tried it on the bike due to a lack of knowing what to use as a timing signal. I wanted to trigger it off of cam timing. It seamed to work out "in theory and on the bench".

If I'm reading it right, the Ecotrons setup is designed around a narrow band Oxy sensor so you are limited in the AFR tuning. For their asking price, they are giving you a lot of necessary stuff.

On our bikes, I don't see any real advantage with the FI except for altitude changes and the COOL factor. Those of us that have dirt only models would have to add a battery and charging system. I don't know how the trials bikes get away without the battery.

Ride on
Brewster

 

In my case, I highly appreciate:
- no gas spill when you lay the bike down;
- no problem with carb venting when you cross rivers or mud holes;
- better fuel economy at reduced throttle, while not compromising the performance at full throttle.
- I know nothing about jets, thus it's real easier for me to tune my bike;
- less prone to "dirt in the fuel" problems (at least, I hope).

There are cons too, the main one being the reliability factor...

Batteryless FI bikes exist, it's just a little more complicated to build an ecu for that. MX bikes all have digital CDI nowadays, and I guess the alternator could accomodate FI without problem. Typically those batteryless FI bikes require one kick to charge a capacitor to condition the FI circuit. The bike is ready to start on the second kick. At least it's the case for the KX250 and KX450, which are FI since 2010 (batteryless).

 

Nice job there RayCour , congratulations !
It´s no wander you are a little upset that you didn't see more horsepower , you only went from 34 to 35 mm . Here is a hint : The WR 250 has a 38 mm throttle body and makes 28 HP , the KXF has a 43 mm throttlebody and makes 35 HP , the CRF has a 50 mm and makes 40-something ...
I've bought a 50 mm CRF body a few months back , I hope I will have the time this winter to put it on . It will require also an intake port modification and an airbox mod . Due to various reasons I wasn't able to even start the bike for the last month or so , hope that will change .
One last thing , you have sharp edges in the throttle body , you do not want any sharp edge in the air duct , think that it needs to have the shape of a "trumpet" .

 

Thanks Marcelino,

35mm is only where it enters the cylinder head adapter. I could have made it 36mm at most. Behind that it is larger (>42mm). One would need to build a head adapter too for larger than 36mm there. But I expect the head port and valves will limit anyway what can be achieved. Do you think I'm right with this?

Yes, but they have bigger bore/stroke ratio too, bigger intake valves and probably larger intake ports.

Wow, that makes for a very interesting project! Let us know how it comes up...

You're right that my TB is not optimal in this respect. If a second iteration is done (not sure about that), we will surely look at refining the shape to avoid sharp edges.

 

It doesn't matter if you have a 42 or a 52 behind a 35 mm restriction ( well it matters but only a few porcents ) . The only restriction you should have in the intake duct ( airbox to valves ) , apart from the throttle , is the "neck" of the intake port , on the KLX it should be aprox 65% of the valve area .This is the 90 degrees region above the intake valves . A 250 can produce only a certain quantity of vacuum , All restrictions will reduce the quantity of air that gets in to the cilinder . Imagine your next shape in the form of a trumpet as I said earlier , is the Ideal shape . You may/will need to make a flange and use a different insulator , the factory one cannot accept any throttle body beyond 35-36 . Use a straight insulator from a WR for example .
All bikes that I cited are 250's , They have bigger static compression because they have larger duration cams . The dynamic compression is abbout the same . You will never get to 35-40 HP but a 26-27 HP is doable with a 38 mm . Don't give up , you have the skills and the leathe

 

Lol, there you are, cranking me

Seriously though I expect enlarging the ports will only benefit on the top end, over 8K rpm. I find it too close to redline to be really benefitting, specially when riding trails. If redline was at 12K or more, then ok...

Actually I have a 300cc jug waiting to be installed as soon as those experiments with FI and custom CDI are finished to my satisfaction. I expect a 300cc will better satisfy my wishes than a boost at 8 to 10K rpm through port enlarging.

Yet your proposal is interesting from an academic pov, plus it might be even more effective on a big bore. We'll see...