Won't rev past 7k RPM

[bochnak]

76' xs360
bone stock except 1 size richer main (140) & richer needle clip position - 1p
carbs are CLEAN! New diaphragms.
Timing & point gap good
Valve adj good
140 psi comp
new air filters/stock air box

When I goose the throttle in 1st, the engine will not rev past 7k RPM. It will just hang there. Plug chop shows lean, went up in main and problem is worse. I doubt I have to go leaner?

Points are a bit worn, probably should change them.

Any advice?

 

[bentwrench]

Stalling at high RMPs at WOT can be caused by the main jet being too large or too small. There are other reasons, but you mention jet size, so it's the first thing I think of.

 

[drewpy]

on CV carbs, you need to set the WOT settings first, then work your way down to 4k which is the transition from pilot to mains.

take your needle down 1 notch first

first make sure the rest of the engine is tuned up first,that's timing valves etc.

 

[bochnak]

I forgot to mention that I changed the main from 135 to 140 with no major difference. I then tried 155 which was too rich. It started to sputter at 3-4k under load.

The needle is already in the 4th notch. Another notch would make it at the richest setting. How would the needle position help me at 7k? Doesn't the needle shine at 1/2 - 3/4 throttle?

 

[drewpy]

no the needle will be pulled by the diaphragm all the way out to feed the top end, where else would the mains get metered from?

you did check your diaphragm for holes didn't you?

 

[bochnak]

no the needle will be pulled by the diaphragm all the way out to feed the top end, where else would the mains get metered from?

you did check your diaphragm for holes didn't you?

Diaphragms are new.

Are we in agreement that it sounds lean? I added a ton more fuel with 155 mains and it started sputtering at 3-4k, so the needle is allowing the mains to flow.

 

[Drewcifer]

Check the springs in your float needle pistons. they can get stuck causing that hang.

 

[zvone]

check the gasoline flow. When there is dirt in tank it happens to me also, but I see the flow over the gasoline filter and it was totaly empty at 6500 rpms. So it was time for me to clean tank and gasoline filter. Then it has enough gasoline and turns good....

 

[bochnak]

Check the springs in your float needle pistons. they can get stuck causing that hang.

Everything looks good.

check the gasoline flow. When there is dirt in tank it happens to me also, but I see the flow over the gasoline filter and it was totaly empty at 6500 rpms. So it was time for me to clean tank and gasoline filter. Then it has enough gasoline and turns good....

Flow is good and also tested in prime position.

 

[bochnak]

Alright,

So I tested the following main jets: 115, 120, 124 (dyno jet brand I believe), 130 , 135 (stock), 140, 150, 155, 160.

At first I thought is was lean, so I kept adding jet, until I thought maybe it's rich??? I then kept leaning it out and seamed to run best with 124/120.

The problem is much improved, however not perfect. It struggles to increase from 7-9k rpm. It is worse in 1st gear. I also ended up 1 notch down/richer on needle clip.

 

[drewpy]

Alright,

So I tested the following main jets: 115, 120, 124 (dyno jet brand I believe), 130 , 135 (stock), 140, 150, 155, 160.

At first I thought is was lean, so I kept adding jet, until I thought maybe it's rich??? I then kept leaning it out and seamed to run best with 124/120.

The problem is much improved, however not perfect. It struggles to increase from 7-9k rpm. It is worse in 1st gear. I also ended up 1 notch down/richer on needle clip.

on CV carbs, get the top end right first on WOT.

then 4 k to 7k

then your pilot

float height makes a difference, as it can make the bike lean or rich on WOT