Author Topic: Asbo 24 535 GT update.  (Read 342 times)

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Bullet Whisperer

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on: June 30, 2021, 11:26:42 pm
Earlier today, the owner of Asbo 24 brought this machine, which I tuned for the previous owner, around for me to retard the [Hitchcocks] inlet cam. Here is a short ride after doing so. I believe it would benefit from slightly lower gearing, as it will go past the redline in 4th, but won't reach it in top. I am told it runs higher gearing than standard, but I did not count the teeth.
 B.W.

 https://youtu.be/LflH0yEAyA8


Taurim

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Reply #1 on: July 01, 2021, 08:31:21 am
Nice one  :)

After all the discussions here about the cams profiles and the usefulness of retarding stock inlet cam by 1 tooth, do you think it really brings much benefit to do the same with H's performance cams ?

My 535 engine is already quite peaky although there are other mods on the head and the intake tract. It only starts to pull from 4K RPM with the long intake horn and 4.5K with the shorter one.
So I'm not sure it is useful to push the torque curve even higher in the RPMs.


Bullet Whisperer

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Reply #2 on: July 01, 2021, 09:08:26 am
Nice one  :)

After all the discussions here about the cams profiles and the usefulness of retarding stock inlet cam by 1 tooth, do you think it really brings much benefit to do the same with H's performance cams ?

My 535 engine is already quite peaky although there are other mods on the head and the intake tract. It only starts to pull from 4K RPM with the long intake horn and 4.5K with the shorter one.
So I'm not sure it is useful to push the torque curve even higher in the RPMs.
.
 Thanks, Taurim! Well, it sounds like yours doesn't get 'on the boil' until quite late in any case, for whatever reason, so retarding the inlet timing is probably not on the cards for your machine, unless you have already done so [which I seem to think you may have done]. The two examples I have tuned by fitting carbs, valves and cams from Hitchcocks, as well as shortening the cylinder barrels - a third machine is all done but still waiting for cams - have lost a small amount of bottom end power with their inlet cams retarded, but still pull well from around 3,000 RPM. You could, possibly, consider advancing your inlet cam timing to gain more bottom end and mid range pull, but mind the inlet valve and piston don't get too close to each other, if you do!
 Also, regarding the third machine, this has a carb conversion [Mikuni this time for some reason], light porting etc on the head and shortened barrel, but Hitchcocks have no cams at present and this machine has been waiting for a set. that said, it is running with the standard cams fitted and I suggested retarding the standard inlet cam, but the owner wasn't interested in doing that, although I will be riding this machine soon, with the standard cams in place and on standard timing, so that might be interesting.
 B.W.
« Last Edit: July 01, 2021, 09:16:07 am by Bullet Whisperer »


Taurim

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Reply #3 on: July 01, 2021, 09:59:52 am
I installed the cams "on the dots" after the discussions here  ;)
That's the reason why I carved 2 valve pockets on the piston to be safe because the cylinder barrel is also shortened.
(I took the measurements with some plasticine in the pockets to validate there is enough space for both valves)



Maybe my head porting job was a little bit too optimistic and I loose quite some torque in the 3.5K RPM band ?... It works fine below 3k
The Dynojet module found the engine requires about half as much injection time at 3.5K compared to stock !

I was about to ask you about the latest Asbo 535 so now I'm waiting for your next video  :)


jez

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Reply #4 on: July 23, 2021, 12:55:03 am
   I own 24
Strangely enough I don't think the power up to 3  has changed, feels better if anything. 3 to 4 a touch softer but the bike is better for fast overtakes as one doesn't have to change gear, the engine will rev out further. With the high gearing top speed hasn't changed. The power has moved up the rev band with a bit more go at the very top end.
If I had a 500 unified engine  I don't think the change would suit the bike's character, but it works on the 535
If I were to go long stroke I'd probably run the cam standard timing, but we'll see how the standard crank holds up....
It was a pleasure to meet and deal with Paul.