Jetting time

rd400canuck · May 27, 2020, 04:50:49 PM

I'm not sure what to do... I was looking into how timing affects an engine and no where I can find anything that says too little or too much advance will cause what I'm seeing. I rechecked the timing a month ago and if I remember I was 1.8 btd. I dont have a timing light though... I was using a light bulb and seeing when the bulb would turn on as I rotated the crank and both sides were when the pointer was at the mark that I set with the dial indicator at 1.8 mm.

The gs pump says "up to 10% ethanol" and I am using regular not the expensive high octane stuff. I'm assuming this isnt a high compression engine and doesnt need that much octane.

I'll go check the air filter but as far as restrictions go... it still has to suck air through that rubber snorkel with nostril sized holes in it. Would a free flowing air filter or one that isnt sealing properly cause what I'm seeing?

Thanks guy.. I'm confused! And it's definitely getting more fuel... the needle is now too fat and feels like i need to put it on the middle form the fourth.

m in sc · May 27, 2020, 04:58:26 PM

the filter matters for sure.

10% is normal, or advertised as 10%, thats not it, that -may- warrant 1 jet size, maybe. set timing to 2.0 or 2.1 on a 400.

rd400canuck · May 27, 2020, 06:11:16 PM

Ok... i cut the plugs to make sure I wasnt missing and sure enough there are rings. In shade it looks grey and in sun its caramel-ish. That chop was with the 150's in very hot humid weather today and they are perfectly even both sides.

Included is pics of the airbox set up. Its uni filter but i run the bottom of the stock filter for the two venturis. It sticks up about half in and is compressed when lid is on. Its also oiled a little. I had already doubled checked the leakdown test a month ago or so and again, it was perfect so I doubt there is an issue there.

Now the needle is rich though... so I'm going to put it on #3 from #4 and see how it behaves... If I like it I'll do another plug chop. Then ill time it at 2.0mm and chop again and see what's up. Judging by the plug chops today I think I am still too lean.

Alain2 · May 28, 2020, 07:07:44 AM

If your bike works good with the 150 main, I would leave it.

rd400canuck · May 28, 2020, 01:19:29 PM

Ya.. everything points to it needing bigger mains than anyone expects including me so I'm just gonna run them. The entire throttle range is seamless now.

I just leaned the needle a position back to #3 and did a 1/2 plug chop. The bike ran better.. position #4 got too rich with the bigger main jets. This bike does NOT like to have too much fuel at steady throttle hwy seeds... it chuffs and does like a mild quick surging. Here is the 1/2 chop pics. One with flash and one without.

rd400canuck · May 28, 2020, 01:33:15 PM

The 100% chop has been leaned out by dropping the needle a position. I will put 160's in it when i get them... then i think ill be done... i hope.

m in sc · May 28, 2020, 01:35:15 PM

thats crazy.

however, as is always said: the bike will tell you what it needs. If it works it works.

rd400canuck · May 28, 2020, 01:51:09 PM

Ya i dont get l

I have 175-P2's in there.. I think that's correct. I starting wondering if i had the wrong needle jets in there causing it to lean out.

I'm excited to get jetting sorted so I can finally install my HPI electronic ignition and feel the difference. I'm super curious about that.. I'm almost afraid to, though! The bike is a joy to drive as is... I hope it only gets better. I might wait and bring it with me in Aug to Deals Gapp if you guys are welcoming canucksters across the border then. Also, I wouldnt mind a smaller rear sprocket to be honest. I have the econocycle conversion on it... i feel the bike could benefit from a few missing teeth. Like... maybe drop the revs by 500 rpm in 6th.

1976RD400C · May 28, 2020, 04:29:38 PM

Well, the last thing you have to worry about is a soot fouling problem.

rd400canuck · May 28, 2020, 08:21:43 PM

lol ya... I wont be fouling any plugs

I just picked up 160's and 170's. I have plug chops prolly tomorrow if its nice out.

Edit.... 170s are way rich. It wouldnt pull past 6500 rpm and burbled. I'm starting to think the 150's are very very close. Ive leaning the needle to #3 the 150's came back a little lean looking on the ceramic so I think 155's might be the ticket. Anywho... I have 160's and want to know what they look like so thy are going in for a plug chop.

rd400canuck · May 30, 2020, 02:00:39 PM

This chop is 160 main. Im a little surprised the 170s were the entire insulator and the 160s seem to be a 2mm ring however, it was scorching hot and humid for the 170 chop and today its kinda cool.. It actually felt a little rich I think. It pulls cleanly until it get to 7000rpm then I think I felt it trying to go higher but i felt the smallest sensation of burbling. I also think the needle is the tiniest bit rich.

So... i dunno. I think the 150's might be the ticket. I'm never going to be full throttle for more than a few couple seconds anyways.

Question... is there a noticeable difference in something like a 150 to 155 ? I'm under the impression a jet with a 5 at the end is a half jump and only for really really fine tuning.

rd400canuck · June 01, 2020, 12:11:48 PM

Alright, I m done with plug chops and jetting. When a 170 drowns the motor and ceramic and a 160 gets me a ring (but still burbles a little at 7000 rpm) I'm beginning to wonder just how accurate plug chops are in this motor. The discrepancy between the 170 and 160 doesnt make any sense to me. It could be me doing something incorrect but I do the plug chops the exact same way every time.

That being being said I am going with 150's, needle on #3 position and a 27.5 pilot at 1/4 out (slows idle but this prevents it from bucking on decel).

With these settings my bike pulls cleanly, steady state cruising is smooth (no chuffing) and the pull is linear and proportional from off idle to wide open. I'll keep my eye on piston tops (right now they are almost clean from being lean) and will add my CHT displays when they arrive but for now jetting is done in my books.

Thanks for all the help everyone.

rd400canuck · June 02, 2020, 05:08:33 PM

Me again

Im so dumb i should have done this from the start.... i went out and bought a timing light... the timing was so retarded it wasnt even funny. Perhaps an entiee millimeter. I set it to 2.2mm and went for a ride and major difference. Befoee the bike wouldnt rev past 7200 in firat or second gear rpm now it will spin past 8500. Setting the timing with a little bulb isnt accurate afaic once the engine is running.

Once the rain lets up im going to do plug chop again and hopefully the results dont confuse the hell out of me anymore.

m in sc · June 02, 2020, 05:32:13 PM

that would explain it.

Alain2 · June 03, 2020, 07:52:00 AM

Quote from: rd400canuck on June 02, 2020, 05:08:33 PM
Me again

Im so dumb i should have done this from the start.... i went out and bought a timing light... the timing was so retarded it wasnt even funny. Perhaps an entiee millimeter. I set it to 2.2mm and went for a ride and major difference. Befoee the bike wouldnt rev past 7200 in firat or second gear rpm now it will spin past 8500. Setting the timing with a little bulb isnt accurate afaic once the engine is running.

Once the rain lets up im going to do plug chop again and hopefully the results dont confuse the hell out of me anymore.

I'm confused, timing is timing no matter what method you use to measure it.

Would you mind telling me how you timed your engine using the timing light?

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Jetting time