81 400 project

Just figured out the search button on mikes xs looking for jets just wanted to bounce this idea off someone to see if they have any advice

For the pilot I'll order the next two sizes up a 45 and 47.5

For the main a 137.5 and a 140

I'm hoping those should do the trick because the 8.00 shopping

Any suggestions?
 
Mikes sell aftermarket jets from china. I have found them to be inferior to OEM mikuni jets. I would look for genuine ones instead. There is a site called jetsrus.com that sells real mikuni jets. If you have any motorcycle shops in your area they should carry mikuni ones also. I would start with stock jets first and set your pilot mix screws a 3-4 turns out and drive the bike. Do plug chops to see how it's running. Most people way over jet these bikes. You will also need to take into account your mid-range rpm's by adjusting the jet needle with shims. Raise it for more fuel if you need to.
 
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Theres a couple threads here that ive posted in, or started about jetting. Real Mikuni jets will always a brand stamp on them so keep that in mind. I prefer Jets R Us.

I have a collection of jets from when I was tuning. I think you should pick up a minimum 3 different sizes unless you really know what you need. Go up/down one size, and get another jet maybe 3 steps up, and another 3 steps down. It took me a while to get the bike where it felt best. Skipping steps on the jetting made the changes more drastic, especially when it came to plug chops. This helped me a lot when it came to "getting to know" the engine and what to look for.
You will probably find more than one size that you would accept. Then you need to do needle height, and then the float. Do not change anything else until you decide on your main jet.

I think the main jets kick in around 7k, so you will need a safe stretch to do full throttle redline runs lol.

Timing and valves need to be good.

On second thought, maybe go maximum 2 steps down at first. Going up too far isnt as bad as going down too far.
 
Lot of good advice there! It'll be a bit before I can do a on the road test I still need a new tire in the front and a few odds and ends. I'll call some shops in the area and see if they carry the jets this week.
 
Had a moment to play with the bike got the carb boots back on and tightened down properly it's running on both cylinders. Let it warm up and it's 4 1/2 turns out on the mixture screws it'll rev up but it hangs at a high rpm for a few seconds. Pulled the plugs and the tips had a white "dust" look to them.

But on a good note it sounds great with both cylinders firing
 
Make sure you sync the carbs with a manometer after a valve adjustment.
 
Found a store on eBay that sells mikuni jets for a decent price under $4 per jet and then only 3.50 for all the shipping. Niche cycle store on eBay showed up 2 days after I ordered


Ordered a couple different sizes but saw a few people on here with similar set ups using 45 pilot and 140 main so tried those first. Started with the mixture screw 3 out.

Started up the second kick and runs soooo much smoother and better now. Reved up quick with a slight idle hand so turned out to 3.5 turns and that did the trick.

Gonna hook the tach up and really start dialing it in and hook up my vaccumn gauges make sure it's as balanced as I can get it.
 
Put air in the front tire and took a mini test drive around the property. Holy cow does this bike move. It's going to be quite fun on the road. Still a good ways to go but getting there!
 

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