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CB750
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First ride misery.
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Topic: First ride misery. (Read 15215 times)
Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #15 on:
July 31, 2011, 10:21:26 PM »
Jets will get changed, but i dont think there anything to do with the main issue.
No leaks on inlet rubbers.
Ill try using the battery off my car, its easy to isolate the ignition system from the rest of the bike. Ill give it a go.
Cant retard it enough to get it right, it seems to just do what it damm well pleases LOL.
Trying to get an advance unit for the stock points, i think going back to points will solve this.
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Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #16 on:
July 31, 2011, 10:26:48 PM »
Speaking of the jets, i dont seem to be able to find any 105 mains.
I guess im just looking in the wrong places, or being blind!
Any pointers?
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Spitfire
SOHC Master
Posts: 1940
Re: First ride misery.
«
Reply #17 on:
August 01, 2011, 08:42:25 AM »
Here you go
http://www.davidsilverspares.co.uk/parts/by-part-number/
Cheers
Den
Logged
1976 CB750F
1977 CB750F2 In bits
1964 BSA A65R In bits
BigAl (Alan)
SOHC Pro
Posts: 579
Hope its sunny at the weekend
Re: First ride misery.
«
Reply #18 on:
August 01, 2011, 09:08:29 AM »
As Spitfire, DS has the 105 main jet (an old ref No. from 2009 invoice 991142461050) I had refurbed my carbs with complete kits from
www.npr-carbs.com
all the componants where fine except the main jets where 120. On rebuild it was a pig to start (not at all on the kick), overheating, would not tick-over unless RPM was above 2000
Strip down and fitted the 105 main jet's, starts no problem, tick-over 1,100 RPM. I did use a vacuum set to complete the final balance
Alan
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Current bikes:-
Honda CB750 K4 (1974) USA
Honda XL500S (1980) UK
Honda CD175 sloper (1968) UK
Honda CB1100A (2013) UK
www.alans-electrics.co.uk
BigAl (Alan)
SOHC Pro
Posts: 579
Hope its sunny at the weekend
Re: First ride misery.
«
Reply #19 on:
August 01, 2011, 09:11:57 AM »
Correct address
www.nrp.carbs.com
Logged
Current bikes:-
Honda CB750 K4 (1974) USA
Honda XL500S (1980) UK
Honda CD175 sloper (1968) UK
Honda CB1100A (2013) UK
www.alans-electrics.co.uk
Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #20 on:
August 01, 2011, 12:27:30 PM »
Great, thanks.
Odd you had the same issues and the jets solved it, the mains shouldnt be doing anything at 1800 and below.
Did it ever idle right with 120's? Mine idled just fine before.
It even idled with 132's.
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Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #21 on:
August 01, 2011, 02:08:30 PM »
Out of curiosity i checked the cam timing. Can lift the cover enough with the engine still in to see the end of the cam
As predicted, its fine, spot on in fact.
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BigAl (Alan)
SOHC Pro
Posts: 579
Hope its sunny at the weekend
Re: First ride misery.
«
Reply #22 on:
August 01, 2011, 02:27:19 PM »
120 jets, Checked the electric's/timing/points/needle hight as yourself, still no joy! Replaced the main jets to 105 (forgot to mention I changed the air box to carb rubbers, existing had hardend and shrunk) checked all clamps and its been great to this day
Logged
Current bikes:-
Honda CB750 K4 (1974) USA
Honda XL500S (1980) UK
Honda CD175 sloper (1968) UK
Honda CB1100A (2013) UK
www.alans-electrics.co.uk
Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #23 on:
August 01, 2011, 07:13:35 PM »
Spoke to a very helpful tech guy at boyer and he said its either a bad connection in the power feed to the box, or the box is broken.I said about runing it from another batty and he agree'd that would confirm either way.
Run it from my car battery and no difference so the box is indeed faulty.
Logged
Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #24 on:
August 01, 2011, 07:44:26 PM »
If you had no ignition, would you get together a stock points set up, or go electronic bith boyer?
Cant decide whether to perservere trying to get an advancer, or get another ignition box.
Pity i dont have the reciet or it would be replaced under warranty.
Logged
K2-K6
Grogu
Posts: 6044
Re: First ride misery.
«
Reply #25 on:
August 01, 2011, 09:12:19 PM »
In my experience they are a good points system on these and very rarely give any significant problems so it's not a bad route to follow and easy to work on too.
As far as I'm aware the electronic kits may have an advantage at high rpm/compression/competition motors but it's far from clear cut on a standard road motor that's not thrashed to hell, so you're unlikely to miss-out much if you do run points.
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Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #26 on:
August 01, 2011, 09:18:49 PM »
Thats what i figured.
Points are more complicated, well, more moving parts, but simple to work on and fixable at the roadside.
EI is all well and good, but my bikes just proven it can sometimes just break and leave you stranded.
Ill carry on trying to find the advancer.
Anyone know if a cb400 advancer will work? It has a different number (333 rather than 300) but the difference could be in the cam, which i have, springs/weights could be the same.
Logged
Graeme77
SOHC Member
Posts: 208
Re: First ride misery.
«
Reply #27 on:
August 06, 2011, 10:38:30 AM »
It runs!
Fitted the mech advacne and points (spark a little, condensors are good, ill order new points) set the timing up, charged the battery hopefully for the last time
and it runs spot on. Idles nice at 1200, picks up well, sounds nice.
Charging ok, got a smidge over 14v at 4k. I might tweek that up a tiny bit more.
Fitted 105 jets and a new air filter this morning too.
So, second ride in a bit and hopefully it will pull well.
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ritchie-k1
Newbie
Posts: 31
Re: First ride misery.
«
Reply #28 on:
August 06, 2011, 11:09:22 AM »
Well done! you'll enjoy it a bit more now
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Spitfire
SOHC Master
Posts: 1940
Re: First ride misery.
«
Reply #29 on:
August 06, 2011, 11:35:36 AM »
Great news, enjoy !
Cheers
Den
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1976 CB750F
1977 CB750F2 In bits
1964 BSA A65R In bits
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First ride misery.