New jets, new problems

[nitrofish1]

Hey guys, had my bike running good last year, was running a tiny bit lean in the mid range, and rich in idle and low (father drilled out pilot jet too big after a tune), now I installed jets one size up (145 mains and 45 pilots now) from factory to accommodate my MAC exhaust, and it idles high at stops (3-4K), but after a while will settle down.

Backfires after WOT released as well.

Not sure where to start, air screws maybe? Sounds rich.

I have 2-1 exhaust but stock air filters, pretty sure I installed the jets correctly (I bottomed them out like the stock ones that came out).

Drewpy says 3 turns out from bottom on the air screws?

I did not change any other jets or setting, only a change.

Thanks

 

[rshutchinson]

I'd say you have an air leak if anything. I'd check for leaks around the boots from head to carb. The main jet seems a bit big but would have to plug chop to know for sure. I am at 145 mains, 45 pilots with pods and open exhaust.


Do the revs hang before coming back down to idle if you are cruising, pull in the clutch and rev it up?

 

[nitrofish1]

They do!

Stock size is 142.5, and it seemed like it could've used a little extra fuel at WOT so I went up one size on each.

Possible that I did nick the boots from the filters to the carbs, I was beating them up trying to get it all in there.... I also need to dig up some clamps for between the filters and boots.

 

[nitrofish1]

When I roll off the throttle, the revs stay around the 4k range, only way they go down is if I sit at a stop for say 10 seconds and it'll go down to normal idle.

 

[rshutchinson]

Stock on the 81 sohc is a 135 main, 42.5 pilot.

I'm not saying your bike may not need a 145 main, but for stock airbox it seems quite high. Did you plug chop to think that it needed more fuel? If anything it could have been rich even at the 142.5 main.

A leak between the filters and carbs wouldn't really mess it up all that much, it's after the carbs that is the issue.

Hanging idles are usually vacuum leaks..

 

[nitrofish1]

I'll have to double check later this week, but I'm sure they're sufficiently tight.

My manual says stock is 142.5? Instead of buying new jets could I just move to pods?

 

[rshutchinson]

Yes, you're jetting would be a great start and possibly just right with pods. You could fine tune from there but my build runs great with UNI pods and the 145/45 jetting.

Take an unlit propane torch around the carb and boots to test for leaks. If the RPM's jump then you've found the leak.

 

[16VGTIDave]

Please note: there are NO "air screws" on the stock carbs. NONE. There are however Pilot Mixture Screws. As the name indicates, they adjust the Pilot Circuit Mixture. Translated from Japanese, that would be Idle Mixture. In for lean, out for rich. Typical staring point is 2.5 turns out from GENTLY seated. If more than 4 turns out are required, increase the Pilot jets to the next larger size. If less than 1 turn out, decrease 1 size.

All adjustments and testing should be done on an engine at full operating temperature. Typically a spirited 15 minute ride is required. The valve clearances should be correct before attempting carb adjustments.

As we often say, clean the carbs, again!

 

[nitrofish1]

Please note: there are NO "air screws" on the stock carbs. NONE. There are however Pilot Mixture Screws. As the name indicates, they adjust the Pilot Circuit Mixture. Translated from Japanese, that would be Idle Mixture. In for lean, out for rich. Typical staring point is 2.5 turns out from GENTLY seated. If more than 4 turns out are required, increase the Pilot jets to the next larger size. If less than 1 turn out, decrease 1 size.

All adjustments and testing should be done on an engine at full operating temperature. Typically a spirited 15 minute ride is required. The valve clearances should be correct before attempting carb adjustments.

As we often say, clean the carbs, again!

So far I have not touched any mixture screws, but I will double check how far out they are turned, my jet change is not too drastic imo.

I cleaned my carbs once a few years ago, but I right lightly throughout the year, never had any issues with signs of dirty carbs, always drained and dried for winter. Did a valve adjust earlier in the year, they increased maybe .01" throughout the years that I've had the bike.

I will also try re-seating the carbs in their boots, I got pods on the way now.

 

[rshutchinson]

What pods did you go with?

 

[nitrofish1]

What pods did you go with?

Emgo cone type

 

[rshutchinson]

You'll need to cut some of the rubber lip off on the inside. It blocks air jet passages. I just did it today on another engine.

Before

After

 

[nitrofish1]

You'll need to cut some of the rubber lip off on the inside. It blocks air jet passages. I just did it today on another engine.

Before

After

Thanks, I'll let you know how it goes once they come in and I get it all settled/checked out.

 

[xschris]

I would send back the emgo's. They are the worst filter/screen you can have next to running no filter at all. Either use stock or uni's or real K&N filters. Also keeping the stock H-pipe make a big difference. Check where yor idle mix screws are at and make sure the carbs are synced with a manometer. Check also for any holes or cracks in you diaphragms.

 

[16VGTIDave]

I'll second what Chris said. Those Emgo "filters" are crap. Worse than that actually. They don't filter well, obstruct ports on the carbs, and cause turbulent airflow into the carbs. Just because some hipster wannabe "builders" put them on their $5 budget built photo shoot wrecks doesn't make them any good.

There is lots of info here about cleaning carbs and adjusting them. The hanging idle issue is often caused by dirty Pilot circuits (idle mixture).

Nitro - RTFM. (Take that the way your crew chief/DoM would say it, or as Read The Forum More. Your choice.) [emoji6]

 

[nitrofish1]

OK so been a while, weather hasn't been cooperating enough to work on the bike much, here's what's happened so far...

Have not installed the EMGO filters per your suggestions, trying to troubleshoot on stock intake filters, still have MAC 2-1 exhaust.

Father came over to help troubleshoot, what we're dealing with now is still idling around 4000rpm when hot, checked multiple times for vacuum leaks and found none, jets are at 42.5 pilot (+1 from stock), and 135 mains (stock size), tried to iron it out at 1.5 turns out on the mixture screws with little luck, did a little searching and tried it at 3.25 turns out with no luck there either, wondering if I need to go up to 4 turns out or so to get it to settle down. Right now it is still acting "lean", lots of exhaust popping and rpm's won't settle to normal when I roll off the throttle, also there's a dead spot in the acceleration around 5-6k rpms.

Should also mention that we did set the float heights, and synced the carbs, I also did valve lash just last year after a few years of riding the bike without adjustment they were only off by about a thousandth.

Thanks