137 Main Jets Verses Drill Size

[Winterhawk]

Suspected my bike to be running way to rich on the main jets. I adjusted the float height to 26mm. The floats were lower than this. I removed the main jets which said 137 on them. I was looking at my jet assortment and found a drill bit that slid perfect inside my 137's. Then found other 137's I had at it would no fit being way to large. What gives? Did I get into a batch of K&L jets that the sizes differed?Anybody else seen this comparing jets with a drill?
I put the smaller 137's in place of the larger 137's. Now I haven't a clue changing 2 things at once as to how it runs better or worse. Testing it after I sync the carbs

[bikerphil]

Dynajets also use a different numbering system than Mikuni. BTW, a genuine Mikuni 137.5 stock size main jet is the size of a #54 drill bit. HTH

[Cyclechrist]

Dynojet stage 1-3 and first time on

I have the same ? I have a 79 XS1100 SF and picked up a 1980 XS1100 Dynojet kit
Came with 3 stages
Main Jets #DJ124, #DJ128, #DJ138

Pilot Air Jet #DJ190 ?(not the right type of screw set) Almost matches Pilot air #210 from stock. I'm with you on the drill size.
Slide drill DD#39
Fuel Needles DNT604 set at groove#2
Adjusting Washers DW0001
E-clips DE0001
Plug Drill DD#5/23 did not need
ScrewDS0001 did not need

Start Fuel Mixture at 4 turns out

Have in the stage #2 right now preforms nice. lacks on the climb with two people a little (I've got a lot of weight on my fully dressed out cruiser with Big saddle bags and full forward controls off of a HD sportster. Did some of my own fiberglass rear fender to the floor.

Did some custom work on stock Air box. I Have a K&N Air filter in box with both top and bottom open for greater air in-flow... added some fun with 2 Hyper-charger bodies with 1''.3/4 open on each side looks sick!!! Working on putting in the butterfly's with a direct link or I may try some vacuum pods(Chargers where cases only with K&N air filters as well...

The Fun hits at around 6500 rpm's at 70 she takes off!!!!!!! some air induction

Have not gotten to do much work on the exhaust (But I like the 4 into 2 I am running with 19" extended turn outs gives a full 40'' by 3'' pipe... need to add a balance tube before i ride again. My go for a Cross over if have the money and time.

Just Got My Accel Coil Kit and some Iridium plugs (I'll let you all know when it blows up!)

Last on the Wish list is a 3mm 1196 over bore kit from Wiseco.

Did a nice Celtic paint job but needs to be done over now.
Adding a full front fairing with sound off a FLHX more stuff!!!

OK I did not answer your? sorry

[Winterhawk]

Dynajets also use a different numbering system than Mikuni. BTW, a genuine Mikuni 137.5 stock size main jet is the size of a #54 drill bit. HTH

Thanks Phil. I'll check them out. My number 4 plug is black. The bike runs good up until like half throttle then seams like it wants to cut out. I did repair the pickup wires last night. I guess when I stretched the wires both came apart. No spark on all 4 cyl. I checked compression. 150psi. I did a cylinder leakage test and it matched the other 3. I have a good spark looking at it. Idle and performance is great until about half throttle and 4k or so rpms then it stutters for a little while untill itpicks up rpm's. Advance unit? It does move when I rev it but it seams like it flutters. TCI box? Coil?

[bikerphil]

If your vacuum advance unit "stutters" a bit, you can take an old pilot jet and put it in the vacuum hose to smooth it out.

[Winterhawk]

Thanks. I used my digital mic to find and make sure it was a 54 drill and then found the right jets. I've now narrowed it down to the number 4 secondary wire breaking down under load maybe? Going to check the resistance later. Let you know what I find. I'm sure I have some spare coils and or TCI somewhere, have to look after work tonight. BTW, Rusty, from the former Merriam Cycle just found a mint 1978 XS1100 with only 3,000 miles on it for $500.00. Can't wait to see it.