atp turbo xs1100

[SeaAtp1100]

Anybody on these forums with an atp setup? Just finished a top end rebuild (bent exhaust valve, re-ring and hone) and a bunch of deferred maintenance. Wondering about setting timing, the mechanical advance has a tab welded on, and questions about boost on stock pistons. Trying to make it all show and some go. Took it out for a shake down run yesterday so it’s running, going to the dyno next month and want to get the base settings dialed in.

[SeaAtp1100]

Was trying to figure out why I couldn’t set the timings at “f” I guess they only worried about advanced for this aftermarket kit.

[SeaAtp1100]

[DiverRay]

Stock has a mechanical advance, and a vacuum advance/retard set up. With boost, I think you need to retard the spark as compared to no boost to keep ping and knock down. My guess is "static" is close to stock, and they just chopped the top off the advance and run premium, 91 octane. Stock they run great on 87 octane.

[DEEBS11]

You can also run two base gaskets layered to lower compression. This is another way to reduce detonation.

[Mathh]

That is still a great looking bike, well maintained, looking at it. Congratulations!
I ran an ATP turbokit on my standard from 1982 until 1993. It came from the Kawasaki importer in the Netherlands who had several sets in stock. I mounted it on a brand new XS after I had it run in after 1000 miles. The set came with 4 pages of instructions that said nothing about changing ignition settings. It did say however that you should never go over 8 psi with stock engine parts (like pistons...). I had to run it in again with 0 boost setting and then went to 8 psi. The media wrote about these sets that these kits would add 25-35 crank horsepower and I think that was spot-on. Downside was that a fair portion of grunt this bike is famous for, disappeared below 4000rpm. Well... after a couple of months I got bored and changed boost to 10 psi and on a 20 mile run at high speed i looked in my mirrors and saw a huge cloud of smoke..: 3 pistons had melted! As Deebs11 advised you can lower compression by adding another base gasket but that also lowers grunt a bit. However with some fine tuning and different parts like an aluminum base plate, forged pistons, new ignition, stronger clutch and advancing the intake cam I could run it at 15 psi and from 1982 until 1993 the bike and I managed to ride about 120kmiles through Europe without severe problems. I later fabricated a home built kit with fuel injection that made a huge difference in torque.Good luck with the bike!

[SeaAtp1100]

Thanks for the replies. My friend commissioned me to get it back on the road for him. If it were mine, I’d put an electronic ignition and a mikuni 42 flat slide, and think about taking the head and cylinders off to add a base gasket. After I’m done it’s headed to eastern Washington. I have a cb750 that had the head and cylinder block decked then add a wiseco 836 kit and anything less that 50/50 vp race gas/chevron 92 the thing knocks. Future project is to lower the compression on it and actually take the measurements this time for a copper base gasket.

as for getting the xs as right as I can before the dyno. The factory service manual says 36 degrees at 5200 rpm. Wish I had the original atp instruction or could find them online. Does 30 degrees at full advance sound like a good starting point. I’m targeting boost at 6 psi.

[SeaAtp1100]

Got the external wastegate spring backed off I can hear/feel it actuate when I feed it 6 psi. Road test boost gauge got to 5. I have no idea of what the adjustable main jet needs to be at so I’m driving cautiously until I get it on the dyno

[Mathh]

Swapping to the Mikuni RS42 would be a good idea as the original ATP carb operates in a tiny window (sometimes no window). I always found it hard to adjust both adjustable jets perfectly. Most of the time it was perfect in the higher regions or in the bottom region. I think it is a plus if you can convince the owner to put it on before the bike goes on the dyno. I have a RC Engineering kit which also has a good (Keihin) carb.It has a bigger float chamber, a choke(!) and a acceleration pump and at least one fixed jet. Not sure at the moment. Sadly they are hard to find.

[SeaAtp1100]

My guess is "static" is close to stock, and they just chopped the top off the advance and run premium, 91 octane. Stock they run great on 87 octane.

That got me thinking, I think the mechanical advance was set up incorrectly. Look at the weld in my photo. If they wanted to chop the top off how far it would advance the welded limiter should be on the other end of the counter weight slot on the mechanical advance. I set full advance timing to 30 with the vacuum advance plugged up. I checked timing again with the vacuum advance hooked up again and it advances to 40 degrees at 5000 rpm. I think I’m dealing original installer error and why the bike won’t idle below 1700. I wish I could find the original installation material

[SeaAtp1100]

the weld is advancing the engine even before it’s getting rpm.

[SeaAtp1100]

Filed an aluminum pop rivet on a good used advance for testing purposes. Bike now fires at the “f” Mark, full advance at 30 degrees and idles at a more acceptable 1400-1500 rpms. Just need to find someone to weld the lobe and I’ll remove the rivet. At least now I know how much weld it needs. Also dawned on me that under boost the vacuum advance is out of the equation, did test the diaphragm and it does hold the specified 5.91 in hg of vacuum.

[SeaAtp1100]

Swapping to the Mikuni RS42 would be a good idea as the original ATP carb operates in a tiny window (sometimes no window). I always found it hard to adjust both adjustable jets perfectly. Most of the time it was perfect in the higher regions or in the bottom region. I think it is a plus if you can convince the owner to put it on before the bike goes on the dyno. I have a RC Engineering kit which also has a good (Keihin) carb.It has a bigger float chamber, a choke(!) and a acceleration pump and at least one fixed jet. Not sure at the moment. Sadly they are hard to find.

done! Have an hrs42 on the way with a handful of main jets and pilots.
Carb hasn't shown up yet. Then the fun begins. The rubber mounting flange might work, the studs on the turbo inlet are 65 mm centers, hopefully I can wallow out the rubber flange without affecting the port.

It’s a Harley hsr kit that comes with the air cleaner adapter hopefully the plate I have mounts to it with little or no modification. Figure it should fit since the zenith was on Harley’s as well.

I just guessed on the jets based on what a couple of Kawasaki guys with similar cc'd / year engines are running on their turbo set ups. I’ll road dyno before going to the experts

[Ccitis]

That is sweet... funny I was wondering if the XS had been turboed... now there is my answer. Enjoy.

[Mathh]

Good to hear you found that 42mm carb. It should not be too hard to make (or have them made) a new air filter to carb and carb to turbo adapter plate / flange. Always better to get a perfect fit. That lambda sensor position is questionable. If that pipe is shoved into the mufflers and not sealed or welded it will give false readings as it will suck in fresh air when off throttle (or idling). On my Mr.Turbo kit it even sucked in fresh air through the worn threads of the two holes that hold the heat shields. Great to see at night however when it spewed long light blue flames out of the exhaust when closing the throttle.