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View Full Version : 416 jetting question and overheating problem??



rhandw69
08-13-2001, 09:29 AM
Ok peeps, i have some problems that im searching for help on.

1. I put in the 416 kit on my 400. To break it in i took out my 155 main jet, and put in a 165. I thought that would be fairly rich enought for the break in procedures. I am at fairly low elevation if not at sea level (Tacoma Washington). Im beginning to wonder how will i know if its too lean or too rich. When i rode it yesterday, what i noticed was that when i got on the gas it had a tendencey to pop some, backfire and sputter. Now is this the sound of running rich? The reason i ask that is it really did get hot on me which would lead me to belive it was lean. But as far as performance i always thought when it ran like that that was a sign of it being rich.Hmmmmmm????

2. Why does it get really hot. I just changed the oil, and yes i know it has a bigger piston and all, but man,,,it really heats up quick.
Thanks for any replys,
Rhan

86atc250r
08-13-2001, 10:03 AM
You sound lean.

Don't try to guess at jetting. Read the plug, feel the engine, give it what it wants.

NVR2L8
08-13-2001, 01:32 PM
I upgraded my engine to a 416 as well, including an XR400 cam. I haven't run the stock carb with these mods though, as I also included an FCR carb when everything was done. From what I can gather though, jetting the FCR runs fairly close to the stock carb. With my FCR and running a 50/50 mixture of 111 octane race gas and premium unleaded, I'm at a 52 pilot, needle on the third groove, and 162-165 main.

Since you've upgraded the engine and are still in the process of breaking it in, you'll need to rejet "all" of the fuel circuits. Gabe is right though, you have to read the plug and "feel" what the engine is asking for. Also keep in mind how it reacts to throttle position and not engine revs so you're jetting the right circuits correctly. Do some research here on Exriders and on the 'net so you can recognize a lean or rich running engine. Lastly, the best method I've found that works very well, is to over-jet each circuit one at a time, and then work downward until you have the best response and plug condition.

NVR2L8
08-13-2001, 01:46 PM
I forgot to mention about the heat problem...

If you're running lean, you'll definitely be running hotter than normal, and that goes for both a stock or modified engine. After I had the mods done and got it properly jetted though, I also noticed it heats up quicker and runs a little hotter than when stock. I guess that's just a characteristic of the increased displacement and the fact it's an air-cooled engine. I haven't had any heating problems when trail riding though...the only time I've got it really hot is when racing at the dunes. Just get it properly dialed-in, run a good quality oil and change it often, and you should be okay.

rhandw69
08-13-2001, 02:45 PM
Ok, thanks all for the help, i guess whats confusing me is the fact of how I jumped up from a 155 to a 165 main, and how it then could be too lean. Hmm??
NVR2l8,,,what size spark plug are you running in yours, i think ill try that appraoach tonight when i take it out again.
Also, i put in synthetic oil for the break in,,,
now this weekend i would like to change it, but what exact oil should i use.
So am i understanding this correctly,
bad power delivert at 1/4 to half throttle is to rich, and bad power from half to full is too lean.
Do i have that correct??
Thanks
Rhan
416,
WB E Series
K&N
WB Rev Kit
More to come once we figure out the jetting!!

08-13-2001, 03:34 PM
Did you say that you put in synthetic for breakin?
If so you may not want to do that.
breaking these in you should always stay with a petro base oil to allow your new rings to set in the cylinder.
The outcome can be a oilburner with below exceptable compression.

08-13-2001, 06:02 PM
Try reading up on jetting and breaking in a new engine at Duncan Racing's Tech Center.

http://www.duncan-racing.com/

later

NVR2L8
08-13-2001, 06:46 PM
Rhan,

Go back to conventional oil during the break-in period. I ran Golden Spectro conventional oil with a new filter for about 10 hours, and then dropped the oil for a fresh batch of the same stuff along with a new filter and ran this for about another 10 hours. Then I switched over to Mobil 1 15W-50. For your break-in period I would use a high quality conventional oil like the one I used, or you could even use Honda's conventional 20W-50 oil.

I'm running the stock plug... I've got some good info from a post elsewhere that will explain why a cooler rated sparkplug won't affect engine temp. Let me know your email address if you want it.

As far as your question about jetting... Bad running at any throttle position doesn't particularly mean you're running rich or lean...it could be either one...and the key to learning how to jet is understanding whether or not that particular circuit is rich or lean. I'm no jetting expert by any means, but I've found it a lot easier to determine when it's running too rich, than when it's too lean.

From what I've experienced and learned, a lean condition can be seen when an engine runs hot and hestitates, skips, or backfires under acceleration. When checking the plug when it's running lean, it'll be tell-tale white on the porcelain. When it's running too rich, the engine will blubber due to it getting more fuel than air. Checking the plug when it's running rich, it'll be black and sooty on the porcelain. The key to understanding whether or not the hesitation, missing, and/or bad running is indicative of running rich or lean, is to pay attention to what the motor is doing at that particular throttle position. When lean it'll skip or hesitate under acceleration and make it seem like you have an ignition miss. If it's too rich it'll blubber as if you're running with the choke closed. Anyway, if all of this has confused you more than anything, then follow my advice of jetting by first purposefully over-jetting. I've also often found it hard to jet based upon the condition of the plug, due to the additives a lot of companies are putting in thier gas. For instance, even if you're running rich, the additives in the gas will often burn off the black deposit and make it appear as though you're running lean.

At any rate, if you know you're too rich on a particular circuit, then all you have to do is work down until it's properly jetted. Start with a 50-52 pilot jet and re-adjust the fuel screw, and see how it reacts when starting it cold. It should idle fairly well, and when warmed up should not bog when slightly opening the throttle from an idle. If you have to go to the extreme end of your fuel screw adjustment (fully out), then you need to go up a size. If you need to almost completely close the fuel screw to get it running properly (fully in), then go down a size. Then move to the needle and lower it a notch to richen it up. See how it runs and adjust up or down accordingly. Then move to the main by installing a large main jet, such as a 170. See how it runs at that throttle position, and move up or down.

Lastly, check out www.hondex.com under the tech tips section. There is a good article there about jetting.