ANOTHER jetting question

RDDave · August 26, 2026, 06:32:26 PM

Stock RD350 except for Bassanis. Foam filter in the box and jetted up to 160 mains using Mikuni brand jets.

Pulls good through the lower gears, plugs are light brown.

But in 5th or 6th about 5,000, it doesn't like to pull on up. Especially when you open it up. It will creep up with a light throttle touch, but doesn't want to pull through that range if cranked open. After it hits about 6,000, it starts to pull pretty good but still has a slight surge.

I have the needle all the way up (rich) and most of the throttle range got better each step richer from the middle groove, but the 5,000RPM area may have only gotten a little better, if at all.

It seems to me that it wants more fuel. But with it already at 155s, I was just wondering if 160s or more is actually too much. If I had them, I would just throw them in, but the 160s are as big as I have.

To sum; in top gears, it doesn't want to pull through 4,500 up until the power comes on and then it hits good but with a little surging. It does okay in the lower gears. If it didn't improve so much when the band hits, I would be less confused.

So, does it sound like it might want even bigger mains or am I going the wrong direction? Are 160s or 170s usually too much for this mild combo?

Thanks so much..........again.

m in sc · August 26, 2026, 07:26:47 PM

drop needle and try 180 mains

RDDave · August 26, 2026, 08:31:27 PM

Okay. 180s it is. Everything indicated to me that it was still too lean. But I was concerned that I was getting too far from the stock jetting with the engine as mild as it is.

And you were right all along; I installed the Tytronic ignition and it has worked wonders. HUGE difference. It eliminated just about all of the problems that I have been dealing with. Frankly, I am very surprised just how much better it starts, idles, and runs all the way around. Even with the mix being off.

Please don't get me wrong; it's not that I doubted what you have told me time and time again. It's that I just couldn't get it through my head that I couldn't make the original point ignition work. It worked well enough when they were new. I thought it would just be a matter of finding and addressing what 50+ years had wrought.

BUT I WAS WRONG! Thank you for not giving up on me. I really appreciate that.

And thank you for the jetting advise.

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m in sc · August 26, 2026, 08:42:05 PM

i ran points on bikes for many years and usually start a project w them, including the last 2 t500s i did. they should work better than they do, but thye age out and the replacement parts just are questionable at best.

I get it, no offense taken . there re lots of really good running bikes with points. Just not in my garage.

glad you got it sorted.

my 1st rd ran specIIs and an open airbox with a uni, i distinctly remember it being 190 mains. 180 shoiuld be darn close, also in my experience, sometimes the clip needs to be one lean with chambers depending how they hit, but i have no experience tuning basannis

RDDave · August 27, 2026, 08:39:40 AM

RDDave · September 04, 2026, 05:06:35 PM

Got the 180s (Mikunis) in and have played with the needle. With the needle one notch below center and with the mixture screws at 1/2 turn out. It starts first kick. The idle is not bad. The mid range seems strong. But it still isn't what it should be in the upper Rs in the higher gears. And the plugs are (I believe) too white. They shouldn't be white at all, should they? More like a light tan?

Is it possible that it is STILL as lean as it seems to me to be even with the 180s?

I now have spare main jets that are too small. And I have a set of tiny drill bits that I have used for my car carbs that are in the range of those jets.

I think I will drill out a pair of jets .005" or so bigger than the 180s to see if it likes it. If necessary, I can continue to drill the jets larger with the bits that I have until I either go too far or find a size that it likes the best. THEN order jets that size.

The bike runs really good now except for a couple of glitches up top. It pulls good through the gears until 5th or 6th in the 5,000RPM range.

What do you think?

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1976RD400C · September 04, 2026, 05:53:30 PM

I'm not too hip on drilling the jets because now you don't know what size you have and the number stamped on them is wrong. How about going to a local dealer, they normally have jets. Bikes with chambers may not pull well at 5000 rpm in high gear. Have you ridden other RD's that seem to run better?

m in sc · September 04, 2026, 06:46:57 PM

there's a,flat spot common 5200 to 6k. also needle and pilot have zero to do with idle or starting

RDDave · September 04, 2026, 07:58:51 PM

Okay. Shouldn't the plugs be more tan than white?

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RDnuTZ · September 04, 2026, 08:06:42 PM

yes, plugs should be more than White after riding it a bit. Are you running the oil pump? Might want to check it's adjusted right and providing enough oil. I don't remember what air filters system you're running?

m in sc · September 04, 2026, 08:32:31 PM

show a Pic. depends how long it ran as well

RDDave · September 04, 2026, 08:58:28 PM

Foam filter. I have checked the pump adjustment and it was good. I have not driven it more than 20 or 30 miles with these plugs, but I have easily driven 100 miles or so (sometimes hard) with the pump at this setting. Wouldn't I know by now if it was getting too little oil?

And the main issue is that there is very little, if any acceleration at 5,000 in 5th or 6th, but pulls good through there in the lower gears. Might just be normal then? I can live with it as long as I haven't caused it. Or it can't be tuned out.

And I will check the pump setting again just to be sure. I'm using Yamalube.

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m in sc · September 04, 2026, 09:08:50 PM

yeah if your hanging around 5k and just stab it, shift down. thats pretty normal. its a reversion thing. crossover helps adjustable timing, flatslides, reed spacers..lol.

RDnuTZ · September 04, 2026, 11:27:10 PM

Quote from: RDDave on September 04, 2026, 08:58:28 PMFoam filter. I have checked the pump adjustment and it was good. I have not driven it more than 20 or 30 miles with these plugs, but I have easily driven 100 miles or so (sometimes hard) with the pump at this setting. Wouldn't I know by now if it was getting too little oil?

And the main issue is that there is very little, if any acceleration at 5,000 in 5th or 6th, but pulls good through there in the lower gears. Might just be normal then? I can live with it as long as I haven't caused it. Or it can't be tuned out.

And I will check the pump setting again just to be sure. I'm using Yamalube.

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wouldn't hurt to open the bleed screw and manually cycle the pump looking for air bubbles in line while you are down there checking adjustment.

RDDave · September 05, 2026, 09:31:02 AM

Thanks guys! I can live with it. I just wanted to make sure it wasn't something that I could adjust out.

I probably won't spring for the adjustable timing. Just too much money. But are the spacers and crossover alone going to have a noticeable impact? Are there any down sides to the spacers and crossover? I actually have an old set of spacers that look like they were made out of a pair of intakes.

If there is a thread that already addresses my questions, please just point me in that direction. I have looked but didn't find a how to or before and after comparison.

Thanks again guys!

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ANOTHER jetting question