Getting a dyno tune with sniffer

[Syscrush]

Hey all.

My bike is currently with Zed at Z1 Cycletech in Toronto to be run on the dyno and have the carbs get what will hopefully be their final dialling in. While he doesn't specialize in vintage bikes generally or CBX's specifically, Zed has a long history with these bikes for both street and race applications, so between his demonstrated expertise and his well-equipped shop, I'm hopeful that he'll get the carbs from their current "good" state to "great".

I'll update here with results once it's looked after. I was very glad to hear how positive he was about the bike when it was brought in. Also, we had a short debrief after he'd had a chance to start & run it the first time - we talked about how it's tricky to start in the cold and how it has a bit of black smoke on startup, etc. then he said "Look, I've gotta tell ya something..." and my heart started to sink until he continued "...that bike sounds awesome! Nothing like those CBX's."

[NobleHops]

Phil, did you ever have the head off and replace the valve guide seals?

My bike has 38K miles, and smokes on startup, but not thereafter. The advice I got from a great old mechanic years ago concerning an alarming (to me) big-end knocking on my ST1100 applies to this too, in my humble opinion, and it went like this:

"Enjoy your motorcycle"

If I have another reason to go in there, I will replace those, but not before. The way I see it I am preventing my pipes from rusting out prematurely YMMV.

N.

[NobleHops]

P.S. The ST1100 is still in the family, had 70K miles on it, runs great.

[Syscrush]

Phil, did you ever have the head off and replace the valve guide seals?

I haven't, but the previous owner did. It has ~25,000km on it since rebuild, but it also sat for 5-6 years before I got it.

For valve seals, it would be blue/oil smoke on startup, not black/fuel smoke, right?

[daves79x]

If your guy can't get what he wants with just the pilot screw adjustment (only adjustable thing externally, and he'll need the special tool), he'll have to go in to re-jet and that's a pretty expensive proposition, especially with the stock airbox. Hope he can help you, but that's the way I see it. Worth a try.

Dave

[Syscrush]

Thanks Dave. He's doing what he can to limit the number of times that the carbs have to come out/apart in order to keep costs under some semblance of control. This includes baseline testing in a few different conditions, asking me a lot of questions about how the bike behaves, and learning what he can from pilot screw changes.

However, I'm assuming that it'll have to go through a couple of rounds of jetting to get dialled in correctly. Yes, it will be pricey, but it's important to me that he get it as good as he can - if corners are cut I'll regret it every time the bike stumbles or pops when it shouldn't.

[wyly]

If there was a design flaw in the CBX it had to be the difficulty in servicing the carbs, it's a very big deal to remove them, and expensive if you're not doing it yourself.

I went through hell with the shop that rebuilt my engine and the servicing they did on the carbs. I removed and cleaned the carbs myself and cleaned every orifice I could find(many were plugged). The shop synced the carbs and used a sniffer device on each individual header.

I'm still not sure the carbs are working as well they should as I have nothing to compare to but it does start very easily on the first press of the starter even on cold days. My Z actually seems to run better on cold days but maybe that's just my imagination.

[Syscrush]

The good news:
F'n bike made 96hp at the wheel. I wonder if that dyno is a bit generous, but that number does kind of fit with my experience.

The bad news:
It blasted a ton of oil out the pipe at WFO and on decel. He's going to do compression & leakdown tests tomorrow and let me know what he finds. Carb tuning is on hold until we get the oil consumption sorted out. Looks like that motor is coming out this winter. Oh well, I wanted it cleaned up & repainted anyhow.

The neutral:
AFR looks OK at WFO, but is super-lean at ~1/4 throttle and below - up to 16:1, which explains some of the driveability issues I've had.

[wyly]

96 at the wheel is impressive for the old dinosaur...did you rebuild the engine?

[Syscrush]

96 at the wheel is impressive for the old dinosaur...did you rebuild the engine?

Previous owner supposedly had the engine built by Scott Miller, who was Jordan Szoke's crew chief when he was winning a bunch of Canadian Superbike championships on Hondas.

But that was more than 10 years ago, and the bike had a combination of ~25,000 km racked up, plus more than 5 years sitting idle.


Honestly - if I didn't know that a stocker made ~85hp at the wheel, I would have sworn that my bike was close to 100 given how it pulls, but knowing that 85hp is healthy and that the bike is lightly modded at most, I always assumed that it just felt faster to me because I'm so excited to be on the bike. :)

[wyly]

Previous owner supposedly had the engine built by Scott Miller, who was Jordan Szoke's crew chief when he was winning a bunch of Canadian Superbike championships on Hondas.

But that was more than 10 years ago, and the bike had a combination of ~25,000 km racked up, plus more than 5 years sitting idle.

Honestly - if I didn't know that a stocker made ~85hp at the wheel, I would have sworn that my bike was close to 100 given how it pulls, but knowing that 85hp is healthy and that the bike is lightly modded at most, I always assumed that it just felt faster to me because I'm so excited to be on the bike. :)

not that I'm an expert on such things but it's normal for an engine to lose hp as it ages/wears, that yours has 96hp is why I asked if it had been rebuilt...from my understanding that would be more hp at the wheel than a new 79Z (if any experts want to correct me on this please feel free)...if the original 79Z had 103 at the crank it's my understanding that the hp was 89 at the rear wheel...the 1980 model had slightly less hp, with 85 hp is your ride a 1980? is it possible you have an overbore engine?

I haven't had my 79 on a dyno but with a fresh rebuild and a overbore bringing displacement up to 1150 it may be approaching 100hp, one tech speculated it maybe between 105-110hp, I have trouble believing that. But like you I have a hard time gauging just how fast it is, in the city I keep the revs down to avoid excessive noise from the pipemasters so Grannys in Corollas leave me behind at the lights but on the highway passing/accelerating away from traffic seems effortless with just a little twist...since I'm 35yrs between rides I can't gauge if it's faster now than back in 1980...

[EMS]

Some dynamometers are calibrated to show "corrected rear wheel hp", which indicates horsepower at the crank. Make sure that this is not the case.
96 hp at the rear wheel should be around 120+ at the crank. Without forced induction, that would mean it has to be a big bore motor with at least a 11:1 compression ratio, i.e.: a 70-71mm bore.

[Syscrush]

not that I'm an expert on such things but it's normal for an engine to lose hp as it ages/wears, that yours has 96hp is why I asked if it had been rebuilt...from my understanding that would be more hp at the wheel than a new 79Z (if any experts want to correct me on this please feel free)...

That is also my understanding.

if the original 79Z had 103 at the crank it's my understanding that the hp was 89 at the rear wheel...the 1980 model had slightly less hp, with 85 hp is your ride a 1980? is it possible you have an overbore engine?

Mine is a '79, and I was under the impression that the 103 at the crank typically translated to ~85 at the wheel. So I was assuming that mine would be in that 85-90 range.

since I'm 35yrs between rides I can't gauge if it's faster now than back in 1980...

Butt dyno is notoriously unreliable, for sure.

[Syscrush]

Some dynamometers are calibrated to show "corrected rear wheel hp", which indicates horsepower at the crank. Make sure that this is not the case.

I asked him a few times if that's actual wheel horsepower, and he said that it is. Obviously there's some difference from dyno to dyno, and even from day to day. I do suspect that it's a bit generous, but this shop has built some championship winning race bikes, so I'd be surprised if it's more than 5% off.

96 hp at the rear wheel should be around 120+ at the crank. Without forced induction, that would mean it has to be a big bore motor with at least a 11:1 compression ratio, i.e.: a 70-71mm bore.

The seller didn't claim that anything that drastic had been done. Given that it's gonna be coming out/apart, I guess we'll know for sure this winter.

[wyly]

Some dynamometers are calibrated to show "corrected rear wheel hp", which indicates horsepower at the crank. Make sure that this is not the case.
96 hp at the rear wheel should be around 120+ at the crank. Without forced induction, that would mean it has to be a big bore motor with at least a 11:1 compression ratio, i.e.: a 70-71mm bore.

so is that a 24hp drop from crank to wheel? I've read elsewhere that it was 14hp drop...not saying you're wrong I'm just trying to find the definitive number.

70-71mm bore what does that translate to in cc displacement?

My overbore that raise displacement by a 100cc, I expect the Wiseco pistons raised the compression as well but I don't know how much.

I was told by the engine rebuilder to expect more mid range with much stronger roll on response