Some jetting advice

The screws are good. Theyre new and I know they are delicate. Ive come to the conclusion that the #25 pilots are too big even though they are what was originally installed on these carbs. I can screw them in all the way and nothing happens, shouldnt it stall or idle very very low?

I ordered pilot jets. They are the #17.5 but the ID number is MIKUNI N151.067. I cannot find non-bleed pilots in the BS30/96 range.

So now I will wait for the jets to get here. Im also considering ordering one of the Pamco ignition units too.. Theyre worth the $100 or so right?
 
Well boo hoo i recieved the jets from Jets R Us and didnt notice i ordered only one of each size!!

On a good note, i managed to dial in the #25 pilot jets and it idles nicely. I have them set about a 1/4 turn out.
 
This is what the plugs look like after about 200 miles on the generic 140 mains.. i put 17.5 pilots in and the idle is good. I know the plugs have been through all of my tuning bits but the 7k stumble at full throttle is still there.. the plugs tell me that its still lean and surging for fuel at full throttle...? Im gonna put bigger jets in and go get new plugs. Keep in mind that im still breaking in a fresh bore/hone with original yamaha rings. There has been some oil consumption. I want think i lost a half quart in the first 100 miles
 

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Also, ive ordered a more permanent solution for my exhaust. Should be here soon. Also, im 99% sure im ordering a Pamco ignition today just to elminate the points. Coils are next since they are original and the plug wires since they arent removable and probably made of dust inside at this point.

Points gaps were a bit off so i adjusted them. It runs OK and im not riding it hard anymore until its at 500 miles with no major problems.. Man that first oil change smelled terrible lol and it was filthy. The screen had some flakes in it and what resembled some of the sealant i used for the case halves.
 
Those plugs look fine. The white parts should be clean. I don't think you should be burning that much oil unless something is not sealing right. Your exhaust will have a big affect on tuning.
 
I thought it was a lot of oil too. But ive gone around 150 miles after the 2nd change and filter with almost no oil use.. ive asked some other people that have built engines before and they werent surprised about the consumption. Im not blowing any smoke either..

After i adjusted the points and cleaned them, im pretty sure that eliminated the 7k stumble at full throttle.. but ive been limiting my revs to around 5.5k and been shifting early and keeping a decent load on the engine. I definitley want to renew/upgrade the ignition.
 
350 miles going well...

Ive been having some issues with the points. Getting misses and I think the advancer is sticking and thats why my idle has been all over the place. I just ordered the Pamco ignition with the E-advancer so I can be done with points. Might as well order new coils too since I already have new boots and wires.
 
Let us know how it goes. My 360's right cylinder misfires at low RPMs. Gone through most of it looking for the solution.
Did find that the valve adjustment screws were damaged so those are being replaced.
Might want to upgrade the ignition eventually.
 
Ive had the same problem with my right cyclinder too! I mustve followed my manual when i set static timing after my rebuild, but the points were opening no where near the 10* or even tdc.. my strobe light indicated that timing was good on the left side and the right side was at tdc. I adjusted the right side and it made a big difference. I got it pretty stable but it was still missing and going off mark a few degrees here and there. ive been riding it all over this last couple weeks and i took the points plate off to clean and lube the mechanical advancer. After this i could not get anything static timed right, despite putting everything back the same exact way.. even when i had the timing right, i was clocking the plate all the way to one side and i had no adjustment.
 
Yes use a strobe to set timing if your having issues getting it using the static method. 1200 rpm, warm motor, and LF-RF marks.
 
Now I know why my bike had such big pilot jets installed... Im pretty positive my bike originates from up north in New Hampshire or something.. I rode into work last night which is 40 miles each way. Didnt miss a beat and stayed strong as I passed 500 miles since the rebuild. I did run out of gas which got me nervous for a second, but I flipped over the reserve and it kicked back to life while I was still doing about 50mph.

When I was leaving this morning, I hopped on my bike and put the choke on before I kicked it over. It was between 45 and 50 degrees, maybe down to 40 over the night. The clutch seemed to not grab and turn the engine over. Its almost like I had the clutch lever pulled but there was more resistance.. I decided to use the E-start. Got nothing, kicked and e started again nothing.. I was worried about draining the battery so I just waited for a bit to think and inspect electrical components and make sure everything was dry. Finally I got a pop, didnt start but it was close.. Then finally it started after stuttering a couple times.

So my guess is the original pilot was bigger because it gets much colder up north than it does here, I was having trouble at 45 degrees with a 17.5 pilot..

Is this normal? I thought about doing the the priming technique of kicking it over with the ignition off a couple times to get more fuel in the cylinders. Anyone have to do this when its a bit chilly?
 
In cold weather riding you should use 10w-40 oil. The pilot jets where not changed for cold weather areas. Most likely elevation. Your choke will give the bike plenty of fuel for starting.
 
Ok so my bike is running OK. Ive taken to work a couple times which is an 80 mile round trip at highways speeds. I kept it around 6000 in 6th, occasionally slowing to downshift and then run it up to around 75-80mph and trying to counter-act with hills and wind..

I managed to get the timing on both cylinders perfect and they fully advance to the right spot. I replaced the shaft seals in the carbs along with cleaning them. I have the fuel screws set to 2 1/4 or 2 3/4 turns. Adjusted valves again. Been checking the oil level and all is well. I bought new carb boots and installed them. I made a manometer and synced the carbs after I set the fuel mix screws. I have BP7 NGK plugs installled. Proper exhaust also installed.

Im still having an issue and frankly Im a bit embarrassed because I cant positively tell whats going on. If I open the throttle all the way I still get a stumble/hesitation. Theres no popping. As im typing this, im sort of realizing that it sounds like it needs more gas.. The stumble happens at all RPM ranges from 4k to as high as 8k. I havent pushed it past 8k yet because of this.. If I was easy on the throttle I think it would get to redline.

Im thinking if it was rich, the problem would diminish as revs go up?

Current jetting is 17.5 pilot and 140 mains.. Needle is in stock position right in the middle. Should I really buy bigger jets? is anyone jetted to a 150?

I have a set of 142.5s but I feel like if I needed to be richer I would want to go up at least 2 steps to be sure I was correct.

Plugs looked ok too. Im going for a ride later. Ill put some new plugs in and get a pic of them.

Most of my riding is pretty relaxed but also on the aggressive side. It kinda stinks when I cant open it up in 2nd or 3rd gear because it will stumble, but if i give it 75% itll get to 7.5k without a stumble.
 
These are vacuum carbs, dumping the throttle will give you a bit of a stumble if the bike is not setup perfect. There will be a lag in throttle response because you have a bit of a delay between plates opening and slides responding to the motor revs. A rich carb will bog and a lean carb will buck. At least that's what I have found with these. I have been running 132.5 mains in my xs400 carbs with xs360 carbs. Even with uni's and mac mufflers. When I started using xs360 carbs I started with the 140 main and it was much more sluggish at higher rpm's. 135 was better and 132.5 seems great. I think I could even do 130 but I will stick with this for now as I don't go much over 5.5 to 6k most of the time.
 
Had a nice ride today. I have the idle screw set to 2 1/4 turns out. I was getting more popping from the exhaust on decel and the idle would be OK at 1500 and occasionally start rising as I was stopped at a light. I wont go higher than 2500. Still was the engine was hunting around 1500-2500 and gradually rising when stopped. So Ill back the idle screws out another turn and see what happens.

Today was a really the first day I rode it as how itll be.. Basically everything engine/carb related on the bike has been replaced so Ive eliminated like every possibility except for jetting. The hesitation seems to have narrowed down, It will stumble at 7k and then pull through.. This makes me think that I can raise the needle a notch. I havent gotten crazy with trying all different size jets besides a 135 and 137.5, but I cant imagine this little engine pulling any harder than it does now, despite the stumble. It sounds fantastic when it gets up there.
 
This was after yesturdays ride. Im gonna turn the idke screws out to around 3.5 turns. I think i can leave the 140 mains for now and ill raise the needles a notch to richen up the mid-high range. I may just go 2 steps.. the plug grounds are like ashy white.
 

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