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Messages - neilg
16
« on: February 05, 2018, 01:21:56 PM »
Thanks for your thoughts. I also looked at the F3 thinking that perhaps it was a later mod brought on by F2isms. At the moment I'm inclined to agree with Pete and will probably leave well alone unless anyone has any other ideas or has come across this. Like most on here with F2 experience I'm well aware of the failings and it does seem like a logical mod which is what led to think it might have been from the factory.
17
« on: February 03, 2018, 11:48:19 AM »
The studs are being used for the four caps. Bolts are still used on the center fastenings, they look factory but I've never seen studs used on all four cap fasteners and would like to know whether to leave or swop them.
18
« on: February 03, 2018, 10:21:50 AM »
I am using an F2 top end on my latest. The head I have has 8 studs to support the camshaft towers. The parts lists show the usual mix of 4 studs and nuts and 4 bolts. Has any one any idea if this is a later factory change or is it something that has been modified by a previous owner. Any thoughts?
19
« on: January 16, 2018, 08:57:28 PM »
How bizarre, the listing has been withdrawn cos there was an error... or the owner was found out... ooops cynical me 
20
« on: January 14, 2018, 01:30:38 PM »
4,271 miles? 
21
« on: January 12, 2018, 01:04:28 PM »
This was one of the problems with the old Triumph twins. With the dome shape piston and the spark plug to the side, detonation was never getting to the opposite side to the plug in the combustion chambers . That is why when you change the oil on a triumph twin, you always can smell fuel in the oil, which hasn't been burnt off.
On the Triumph race engines I always blocked off the original plug hole and relocated it to the top of the engine, this gives a better detonation and power 
I had similar but different, (if you get my drift), with my old Air Head BMW. When we lost leaded fuel the pre ignition was so bad I seriously worried about what damage was being done. I had already converted the valve seats but never envisaged this would happen at the time. I ended up twin plugging the heads and fitting Delorto pumper carbs to give it an extra squirt on acceleration. Also the timing unit was altered to give a different advance curve. The carbs were set up on a dyno and since then no problems in the last 15 years or so. (I.m looking for some wood to touch)
22
« on: January 01, 2018, 02:23:38 PM »
Ta mate that's confirmed what I thought was right.... just a little mad moment there.
23
« on: January 01, 2018, 01:49:29 PM »
I'm doubting myself after looking at the parts lists. On the F2 parts the rod is shown with the bearing tabs to the front, ie exhaust side. www.cmsnl.com/honda-cb750f2-super-sport-england_model14689/partslist/E15.html#resultsOn the K2 list it is shown to the rear. ww.cmsnl.com/honda-cb750k2-four-england_model14363/partslist/E17.html#results I would appreciate any thoughts. I realise a parts list is no definitive but as I say it's thrown doubt upon what I thought was correct.
24
« on: November 06, 2017, 12:53:12 PM »
I remember seeing one in Dresda Autos when they had a shop near Clapham Junc. That would have been about 1985 ish. It was painted with the black and red stripes that the 750KZ had. I think it was a follow on from the 750SS with the F2 motor.
25
« on: November 04, 2017, 05:46:40 PM »
How about a pair of F2 forks and brakes. The discs will also have to be F2 as they have a smaller diameter, though check the number of mounting bolts before you go ahead as I think the F2 has one bolt less than the K's, or is it one more...not sure but I have messed about with similar swop. I used an F1 wheel and ended up having the discs machined down as F2's didn't fit the hub. Gawd knows what pattern the 750A has. Interesting stuff.
26
« on: November 01, 2017, 05:17:12 PM »
Not K7/8 as they were spoked wheels.The front wheel could be F2 not a DOHC as they did not have the black plastic bits on the spokes which were also ribbed and polished. My guess is they are from a late 750 Hondamatic the last lot had comstars and the headlamp brackets also look the same along with the badge on the bottom yoke. As in https://www.cmsnl.com/honda-cb750a-750-hondamatic-1978-usa_model7237/partslist/
27
« on: October 05, 2017, 12:11:25 PM »
For info, a Delta Part is one that is an updated modified part but still carries the original part number. Or in other words it's a modification done quietly by the manufacturer. So in reality if you buy a NOS part unless it's an obvious mod you might get either an updated piece or an old inferior piece with no way of telling just by the part number.
Thats correct. When I did my guides I had to get them one at a time from all over the place. I ended up with three the same and an odd one all in sealed Honda bags with the same number. The odd one was an original part so I had to source one more Delta item to do the job. Sneeky way of avoiding warranty claims.
Can I ask what was the difference and how were you able to distinguish which is which?
28
« on: October 04, 2017, 05:17:50 PM »
For info, a Delta Part is one that is an updated modified part but still carries the original part number. Or in other words it's a modification done quietly by the manufacturer. So in reality if you buy a NOS part unless it's an obvious mod you might get either an updated piece or an old inferior piece with no way of telling just by the part number.
29
« on: October 03, 2017, 10:38:23 AM »
The location of springs and the top of the valve stems would have stayed the same the slight change in angle would affect the position of the valve head within the deeper combustion chamber, moving the head slightly higher to allow the bigger valves room to overlap. Hence the exhaust valve is slightly more in a horizontal position, (too slight to see by eye I would imagine). This in effect threw out the geometry so the stem is pushing to one side in the guide and so the excessive wear. Honda's original cure was to do away with a couple of oil drains which I imagined they hoped would cure the issue.
30
« on: October 03, 2017, 10:05:03 AM »
Piki, the F3 I don't think you'd tell it apart from a F2 as they're essentially their same bike just moved the name along one notch, did the same with the K7 to K8 as well. Think USA only.
Roy, I know it's recorded some places ( I've found it mentioned in contemporary road tests) that the F2 used different valve angle but I can't find anything official that says that, don't know if anything exists.
I've seen the two head's apart but never next to each other to make a comparison directly. The F2 has bigger fins as far as I know but it just doesn't seem to me that the valve angle changed, after all its only 3mm on exhaust and 2mm on inlet. I'm not certain of it but certainly intrigued if they did change it.
Also, more time ago than I want to remember, a friend ran what I thought was K2 cam gear on an F2 head to replace a damaged set, or at least that's how I recall it. I don't know how true that is but would obviously not be possible if the valve were moved.
They also seem to be in the same place inside the tappet adjust caps with the rocker covers being the same part it seems.
It don't know if anyone else on here has for example the rocker part numbers to compare perhaps.
I believe the valve angle would have had to be wider due to the deeper combustion chamber in order for the valves to fit the shape of it. Also this would gain full advantage of the cross flow effect. In a way it shows that the original CB750 SOHC design was spot on and later attempts to "improve" stretched it to the point where DOHC were the only way forward.
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