Found a torque monster within my bike (dyno charts). Cone Engineering muffler update

[zrx1100]

On my continuous journey of tuning intake and exhaust for the 700cc project (https://www.xs650.com/threads/700cc-kit-with-a-shell-1-cam-in-a-78xs650e.65405/#post-819839) I have stumbled on what this motor may be capable of by removing the 26” commando mufflers that I bought for the project. Here in the latest iteration.

I have removed the airbox and substituted it with UNI pods. The headers are 1.75” which were sleaved down with Torque inserts at the exhaust port and 1 3/8” TPOs from MMM. I ran out of mains and running lean, but even when I fix that I don’t think the performance will be better than what I got with the stock air box and stock headers in the link above. But look at what happened when, for the hell of it, we removed the commando mufflers

Quite incredible…. Look at that mid-range... The bike is lean above 6K and had I had 145 or 147.5 mains on hand with me, the top end would have kept climbing. So now I would like to rethink what I use for the mufflers and welcome knowledgeable suggestions. If anyone has had experience with 18” cone engineering megaphones (straight through or the quitter version https://www.mikesxs.net/18-in-stain...html?fits-motorcycle=Yamaha/XS650/XS650E/1978) or the https://www.mikesxs.net/17-2-in-sta...html?fits-motorcycle=Yamaha/XS650/XS650E/1978

Or emgo/heiden tuning 17” with removable core. Appreciate your feedback. Maybe I need two sets of mufflers, one for the week and the other for the weekend

Here is the dyno sheet for reference: we did not rig up a way to hold the sniffer as it was late in the day and I was way over my booked time. The main on here is 142.5

here is the run with mufflers:

 

[zrx1100]

Here is the comparison vs stock (in gray) measured on the same dyno before I started the project. Have bigger mains and new mufflers on the way. will update.

 

[drgonzo]

That's some nice progress and that midrange hit looks juicy!

 

[zrx1100]

Also setting up a wideband sensor with bungs on both headers to tune.

 

[5twins]

I'll bet those are going to be pretty loud, lol.

 

[zrx1100]

Such is life lol

 

[zrx1100]

checked them out at idle. Not bad at all. ~85db 5 yards away vs 80db for 26” commandos.

 

[drgonzo]

And when you twist it?

 

[zrx1100]

And when you twist it?

TBD. My next step is that I need to weld on some brackets and bungs for the wideband sensor

 

[zrx1100]

And when you twist it?

The db did go up to 94 at start. Here I put my phone down in a measurement mode before I started the bike. You can see the max db on start with the choke on and then settles down to 85

 

[zrx1100]

So the numbers are in for the 700cc setup with UNI pods and cone engineering mufflers:

Got close to 52 hp on one of the runs and 47 ft-lbs. The numbers are excellent and the cone-engineering open core mufflers well captured the power I saw when run without mufflers all-together. Great mid-range and, overall great improvement over commando mufflers, and the original stock configuration.

A couple of things remaining:

• There is some sort of resonance that is creating reversion and a hole at ~ 2500 rpm. Could be all the expansion and contraction of gas from TPOs and torque incerts. In retrospect, should have just bough 1.5” pipes to start with
• The main jet is still a bit small. 152.5 or maybe 155 would be better. the right cylinder is running a bit leaner, so maybe 152.5 on the left and 155 on the right.

All in all, the results are very good. Other than the hole at 2500 rpm. But had I not had the wideband installed, I would not have known about it. The bike flies.

 

[5twins]

If you retard the timing a couple degrees, it may run even stronger. At least that's my "seat of the pants" impression after doing it on both of mine. Set the idle timing at the right side of the idle timing "range". That will put full advance at about 38° instead of 40°.

What you're actually doing here is reverting back to the original timing spec these bikes first came with .....

 

[zrx1100]

If you retard the timing a couple degrees, it may run even stronger. At least that's my "seat of the pants" impression after doing it on both of mine. Set the idle timing at the right side of the idle timing "range". That will put full advance at about 38° instead of 40°.

View attachment 328757

What you're actually doing here is reverting back to the original timing spec these bikes first came with .....

View attachment 328758

thanks for the suggestion, 5T. I was thinking of retarding a bit again. Previousely I did not see much difference on one of my setups (see below), but was thinking about trying it again. Seems to be a consistent advice from many sources.

 

[Jim]

When I was working on the Gonzo ignition mod I played with the advance a bit. Going all the way down to 35° advance didn't seem to affect power at all. 'Course mine was a stock engine, but it felt just as strong at 35° as it did at 40°.

Read up a little and most modern auto engines are between 30 and 35° advance. Very few go all the way out to 40°. I think the modern gas formulations have as much to do with that as anything.

 

[zrx1100]

When I was working on the Gonzo ignition mod I played with the advance a bit. Going all the way down to 35° advance didn't seem to affect power at all. 'Course mine was a stock engine, but it felt just as strong at 35° as it did at 40°.

Read up a little and most modern auto engines are between 30 and 35° advance. Very few go all the way out to 40°. I think the modern gas formulations have as much to do with that as anything.

Those are exact same that I heard from sasche ignition folks. They advise to retard the spark in all of their ignitions

 

[5twins]

I don't go all the way down to 10°, I only go a couple to maybe 12° or 13°. I did it originally to alleviate some pinging I was getting in the hot weather, but I think the bike runs better this way, especially at higher RPMs and speeds. Like I said, set the idle timing over at the right slash mark of the "range", that will put you at 12° or 13° idle timing, about 38° full advance.

 

[arcticXS]

checked them out at idle. Not bad at all. ~85db 5 yards away vs 80db for 26” commandos.

Nice sound! I have been considering the longer (26 or 28") peashooters from Cone Engineering for a long time!