I am very curious as well.
Wedge Friday, June 5th, '26...
- Thread starter ST1100Y
- Start date
Spent yesterday in the shed, ST wrenching...
learned that, compared to EC versions, the US/CN spec cams are missing at least 1.2mm height on the tip of the lobes...
... considering lift & timing this is a lot!!
So what are the engines rated over there? 72HP?
I am very interested in your claim that the EC cams are 1.2mm taller in height than the US/CN spec cams. If I am reading your post incorrectly, I apologize; please correct me.
According to Honda (and my own measurements) the lobe height on the US/CN intake cams are one of the following:
36.480mm (49 state and Canada type)
35.680mm (Standard California and USA ABS/TCS)
So, if I take the height measurement of 36.480mm, then add your claim of "the US/CN spec cams missing at least 1.2mm height on the tip of the lobes", that would put the EC version of the intake cam at least at 37.680mm in height.
Since you are making this claim, one must assume that you measured your cam lobe height. What was your measurement?
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OP
OP
Yeah, I too was looking at those pages in the w/shop manual...I posted information related to this years ago, but it seems to have disappeared along with most everything else that made this site an invaluable repository of Honda ST knowledge. A lot of it was posted by st-owners who are no longer with us. Now, a lot of that knowledge is lost forever. What a shame.
The ST-1100 service manual for the US/Canada market specifies two different cam profiles:
Here are the cam timings:
I own a 1998 ST1100AW (ABS). This is the California version that has the milder cams. I obtained and installed the more aggressive cams from a '91-'96 Standard 49 state and Canada type. I noticed a performance inprovement; the bike spun more quickly up the tachometer. The reason for this is that the California/ABS-TCS cams (what my '98 ST1100AW came with stock) have zero valve overlap — the exhaust valve fully closes 5° before TDC, and the intake doesn't open until 5° after TDC. There's actually a small window where both valves are closed. Combined with a slightly shorter lobe, this was clearly the CARB-friendly, smooth-idle grind.
The 49-state/Canada cams have about 10° of valve overlap — intake opens 8° before TDC while exhaust doesn't close until 2° after TDC. The intake lobe is also taller and the intake duration is roughly 15° longer than the California cam. The exhaust duration is actually identical between the two — it's just phased about 7° later on the 49-state/Canada cam, which is what creates the overlap in the first place.
What that overlap does in practice: at higher RPM, the outgoing exhaust pulse helps pull in the next intake charge (scavenging), improving cylinder filling and top-end breathing. So the trade you're making is a bit more top-end power and higher-RPM pull, at the cost of a slightly less smooth idle and marginally softer low-end torque. It's the classic emissions-cam-vs-performance-cam tradeoff — Honda literally built both into the same engine family and handed out the mild one to CARB states and ABS bikes to meet emissions certs.
I would be interested to know if the European-market ST1100s had even a more aggressive cam profile. Would someone from the EU market who has the EU version of the ST-1100 service manual please check the camshaft specs against what I posted? Thanks.
Then I was staring at the cams in front of me and figured "... wow, already by an unarmed eye those EC spec cams show wide and tall lobes compared to the narrow and shorter '01 CN ones..."
Measured the cam lobe height (1) and confirmed a difference on the IN lobes of aprox 1mm (likely 0.96mm out the manual)... which seems a lot, which is why at first I slowly and carefully turned the engine over by hand...
Timing is identical to your 49 state model...
I can confirm quicker throttle response/spinning up and more 'grunt' in the low end; larger EC spec (#40 & #128) jets contribute there...
Still like to go in there again and raise idle screws slightly from 2-1/8 to 2-2/8 turns and see what that does...
Time is an issue, the '00 ST also needs a tuneup and carb overhaul before the mandatory MOT...
(and every time I schedule a Saturday for this, ze GF slams me with some "social thing"... there will be a day I just won't show up...
)
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Thanks for the reply and for posting the cam dimension information from your service manual.Yeah, I too was looking at those pages in the w/shop manual...
Then I was staring at the cams in front of me and figured "... wow, already by an unarmed eye those EC spec cams show wide and tall lobes compared to the narrow and shorter '01 CN ones..."
Measured the cam lobe height (1) and confirmed a difference on the IN lobes of aprox 1mm (likely 0.96mm out the manual)... which seems a lot, which is why at first I slowly and carefully turned the engine over by hand...
Timing is identical to your 49 state model...
I can confirm quicker throttle response/spinning up and more 'grunt' in the low end; larger EC spec (#40 & #128) jets contribute there...
Still like to go in there again and raise idle screws slightly from 2-1/8 to 2-2/8 turns and see what that does...
Time is an issue, the '00 ST also needs a tuneup and carb overhaul before the mandatory MOT...
(and every time I schedule a Saturday for this, ze GF slams me with some "social thing"... there will be a day I just won't show up...
Yes, the specs you posted from your service manual confirm that the EC spec cams are the same as the 49 state/Canada type.
The only other differing performance-related item that I am aware is that at least some EC spec carbs had a differently designed slide that the US spec carbs, which is not a surprise given the larger EC spec jets. I have seen pictures of them and had the part number, but have not obtained any. I also wonder if the needles are a different spec also.
OP
OP
Well, I tried hard to find any difference between diaphragms, sliders and needles of the '01 CN and the EC spec...
Came up with none...
Currently rebuilding the '94 EC carb set, two air-cut diaphragms torn, hence taking the whole bank apart to replace all 4 (actually not as hard as everyone warns about, Vessel Megadora Impacta #2 & #3 mandatory though!!)...
Also gives a chance to replace the hardened O-rings of the fuel- and air-rails...
Once you get the hang of it, not complicated at all, all springs back where they belong, etc...
"... we do those things not because they are easy..."
