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Messages - fogrider
31
« on: June 15, 2021, 06:17:17 PM »
Re the main jet O rings, I also installed new main jets that came fitted with new O rings. I was'nt totally satisfied they were sealing fully , when removed and measured, they were 1x4 ( nominal) and , since O rings are sometimes subject to shrinkage in manufacture, they were actually 0.9mm x4, which is a tenuous fit.
I figured 80p for 4 'O' rings was worth the effort.
32
« on: June 15, 2021, 09:23:52 AM »
I suggest you replace the main jet O rings. Even if it's just to eliminate that as a possible problem, it's cheap enough to try. You want 1.2 section by 4.2mm ID. That size is available. The lightest smear of petroleum jelly will help them push in. Don't twist them !!
Make sure they go on the end with the shortest end boss. (it's the deepest location for the O ring.).
33
« on: June 14, 2021, 09:41:52 AM »
The compressions have been mentioned on here, finally got 'round to a check :
cold engine, 150 psi on all 4, give or take 1 psi. Looks OK to me for a mere 9 to 1 engine.
Hopefully the 1.2x4.2 O rings will turn up today and I can put the carbs back on and try the latest changes and adjustments. Trial and error. I think I now know what was going on, soon find out !
34
« on: June 12, 2021, 09:49:17 AM »
1.2x4 should do, as the originals AND the new aftermarkets were 1x4. But, the stretch on 4 may be just a little too much and not enough crush. Cheap enough to try some 1.2x4.2.
I've tried it with and without an air filter, both paper and the foam that was in it. No difference. All I can do is try something else and see what happens. The difference on needles is incredible. I'm going to try the aftermarkets, which made it too weak bottom end, but in one clip richer. At least with the Lambda in I can see the results clearly and it stops me making wrong assumptions.
These carbs seem very sensitive to small changes, I suppose that's a product of a small choke size.
I know it's said these carbs need the original brass bits in, but I suspect there is wear in the needle jet, that would explain the issue somewhat, not entirely sure what size it should be, more research req'd. Must find Deltariders chart again.
35
« on: June 11, 2021, 04:04:53 PM »
After being side-tracked by other things, finally had another run with the original needles back in. That's all the original internals now back in, clip 2, float levels correct. Ignition back to standard. Screws 1.1/2 out.
Started fine , sounded good, had to take the choke off very early (opposite to before) as it was showing very rich on the Lambda reader. Even after 10 miles it was showing way over rich the full range of throttle and yet STILL had a small stumble just after opening up.
Back home, took the plugs out, jet black.
All I've done is put the original needles back in !
The aftermarket needles had made it vastly weak right to the middle range , then too rich top end.
I tried some new main jet O rings, 1.2x4 (on stock, 20p for 4 ), but I'm waiting for some 1.2x4.3 which calculate as the right size (80p for 4 ). Maybe that's the top end richness issue, can but try........
36
« on: June 08, 2021, 08:14:32 PM »
It's a good tip to apply chain lube straight after a ride, while the chain is warm. It lets it run into the links easier. Next ride it has fully dried on and less likely to fling.
Bought some cheap chain lube once and this was the only way I could use it.
37
« on: June 06, 2021, 12:27:34 PM »
Not ON the bike, but out of the sky : heading to work early one Sunday morning along the M62. Empty, I was on my GPZ750 so decided it was an opportunity for a flat out. I was looking down at the clocks ,125 mph, she's still going well, looked up and there's an A10 fighter , extremely low coming direct at me at a very fast closing speed ! Frightened me to death. It seemed as though it was trying to hit me.
The next day a neighbour who had connections with the RAF told me it would be a photographic bombing run. I would love to have a copy of that !
38
« on: June 06, 2021, 09:36:15 AM »
That's helpful, mine are the ones in the lower photo. Don't know what model ref . It would be great to check the size of that air drilling in the carb face before the carbs go back on again. probably correct, but worth checking if they are part of that massive weakness bottom end.
The way it went more and more rich when well up the rev range is strange, especially with that thin foam filter in. That would normally weaken it off . I have read on here that it could be fuel being pulled past inadequate O rings on the main jets. They are new on the aftermarket jets, I will get some better ones tomorrow even though they are are a reasonably firm push fit.
The jets do check out as 98 though.
39
« on: June 05, 2021, 09:20:55 PM »
Just found the reference to a slow air jet - it's in an addendum to the CB550K manual, shows a fuel level of 14.5mm so must be a different version of these carbs.
If anyone's got some 069a's accessible and can measure that small air drilling to the side of the venturi, that would be a
very useful bit of info. My guess is 1.5mm, but confirmation very welcome.
Anyone ?
40
« on: June 05, 2021, 04:59:43 PM »
The reference I saw was to a slow jet, but not stated as idle jet. I assumed it was meant to be slow air jet, I've seen them quoted as 150 and 220. 220 could be for the 750's though.
No problem with the idle jets, original 38's, the long ones you illustrated . They do seem to be nearer 40 though but it idles OK at the right air screw turns out.
I checked the air entry hole which is in the air box side of the carb mouth. I assume that is what is referred to as the slow air jet. It works out as a 180, much more air than a 150.
The original needles are now back in. The difference in diameter at set points amounted to nearly 2 needle clip positions weaker.
The new main jets with their O rings are a firm push fit, but just in case, I shall get "proper" O rings on Monday before re-fitting the carbs. Will put the ignition back too so it's a fair comparison.
Here's hoping.
41
« on: June 05, 2021, 10:41:43 AM »
Deltarider, thanks for the 2 references above. It confirms the slides are 2.5. One thing I noticed is a reference to a slow jet. There is'nt one on the parts diagram so presume it's a drilling. Must check that for size.
Carbs are now off (again ).
Have to be really thorough this time, especially the needles.
42
« on: June 05, 2021, 09:17:54 AM »
The cutaway is the curve cut into the bottom of the slide. 2.5 means the cutaway is 2.5mm deep at its' deepest. The less cutaway, the richer will be the mixture at off-idle openings.
I went from 2.5 to 2.2 as an experiment only to find negligible difference. Goes instantly weak off idle. I'm more used to Amals and SU's and they never do that, however bad they're set up. All very odd.
I expect I'm missing something totally obvious, but what ?
Carbs off again today while the sun's hot on the rubbers.
43
« on: June 04, 2021, 06:41:03 PM »
That's a useful chart, great details and part numbers, only missing the cutaway, mine are 2.5 for the 069a and genuine Keihins. Not sure about the others.
Looked at the old needles, correct part numbers. I'll have a critical comparison of the aftermarket ones, once I've got them out. Sincerely hope that that's it.
Regarding it going very rich top end, will have to check the hole size in the new mains, maybe they're duff too. If these latest changes cure it, I should be able to go back to standard ignition.
Had a belt around Notts and Lincs on the VFR for a day out, nearly 200 miles , a couple of great cafe stops, lovely cake in Tiggys in Epworth. Great ride out with an ex bike cop on his 1300 Pan.
Made a pleasant change from tinkering.
44
« on: June 04, 2021, 04:03:43 PM »
Lambda sender fitted and have had a run about. When fully warmed up, stopped and read the idle, slightly rich. ( on return, I turned the air screws out to between 1 .1/2 to 1.3/4 turns out from 1.1/4 which now reads right ).
Shocking to see that from even the slightest opening of the throttle right up to half open, the weakness was off the scale.
From half throttle on, goes well rich ! I had bought an aftermarket carb kit, fitted the float valves as mine were shot, left the idle jets in, left the needle jets/emulsion tubes in but fitted the new needles. Fitted the main jets as they had new O rings on but were marked 98, whereas the old ones were 105. From the results, I can only assume there is a serious discrepancy with those needles ( in clip 2 the same as original ) and there is almost no transition from idle to needles via the slides.
I'm sure the mains should be 98, had someone already put 105's in hoping to cure weakness ? or is it just the new needles ? Carbs to come off again, old needles back in. Test run again next week.
45
« on: June 03, 2021, 07:07:04 PM »
OK, it's not a usual thing to do, but it likes it, no side effects, just runs better. I think it confirms the mystery weakness at the bottom end. All 4 plugs are identical colours so whatever is causing that weakness is built in, not like one faulty carb.
I altered the slides to 2.2 from 2.5 and there is hardly any difference. I'm halfway through fitting the Lambda sensor and reader. What that shows will be very interesting.
Next few days.........
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