Post by: bladeboy on January 13, 2016, 07:39:19 PM
Can anyone advise me if it's a good idea or not... Cheers
Post by: Bryanj on January 14, 2016, 07:07:11 AM
Post by: Greebo on January 14, 2016, 12:14:19 PM
Hi, I'm thinking of fitting a set of 29mm CR carbs to my 78 cb750,
Can anyone advise me if it's a good idea or not... Cheers
I look into this a couple of years ago before building my CB 750 K6 café racer, so I agree with Bryanj stick with the stock carbs especially if its a standard engine [not tuned]
CR carbs can even cause unreliability for race tuned engines, they are also difficult to ajust in situe.
I finished up putting K&N filters on mine [stock motor] along with re-jetting which took a bit of sorting, but it goes like stink now.... ;D
Post by: bladeboy on January 14, 2016, 09:46:35 PM
Post by: Bryanj on January 15, 2016, 06:44:29 AM
Post by: Greebo on January 15, 2016, 11:13:00 AM
So stick with standard carbs but re jet them .... I was going to put a yoshi cam in her bad idea or not??? Such a grey area thanks for yr input guys.
Don't play around trying to tune the engine you will have a headache with reliability, theses engines dont like tuning, unless its done by a sohc professional specialist & then it would only be good for the track.
I put K7 carbs on my K6, only because the originals were knackered & I'd got a good set of K7 carbs, fitted 138 main jets, needle is on last notch [bottom] ignition timing advance 10 degrees, more power & it runs like a dream.
I have a full spare set of K&N filters as new for sale [for the K6 carbs]
Post by: onethumb on January 15, 2016, 05:24:09 PM
Hi, I'm thinking of fitting a set of 29mm CR carbs to my 78 cb750,
Can anyone advise me if it's a good idea or not... Cheers
I look into this a couple of years ago before building my CB 750 K6 café racer, so I agree with Bryanj stick with the stock carbs especially if its a standard engine [not tuned]
CR carbs can even cause unreliability for race tuned engines, they are also difficult to ajust in situe.
I finished up putting K&N filters on mine [stock motor] along with re-jetting which took a bit of sorting, but it goes like stink now.... ;D
Sorry to hijack but I've got the PhD carbs on my 750 f2 and will be putting cone filters on what jet size should I go to or should I just clean every thing up?
Also is there a rebuild link for the PDFs carbs anywhere?
Thanks again, steve.
Post by: onethumb on January 15, 2016, 05:27:09 PM
Sorry to hijack but I've got the PhD carbs on my 750 f2 and will be putting cone filters on what jet size should I go to or should I just clean every thing up?
Also is there a rebuild link for the PDFs carbs anywhere?
Thanks again, steve.
Post by: yozzer74 on January 15, 2016, 07:49:54 PM
Post by: SteveD CB500K0 on January 15, 2016, 09:04:18 PM
Sorry admin but idiot know how to split the quote thing up. My bad. :-\
Sorry to hijack but I've got the PhD carbs on my 750 f2 and will be putting cone filters on what jet size should I go to or should I just clean every thing up?
Also is there a rebuild link for the PDFs carbs anywhere?
Thanks again, steve.
PhD Carbs? You need a university education to understand them!
8)
Post by: SteveD CB500K0 on January 15, 2016, 09:08:09 PM
Sorry admin but idiot know how to split the quote thing up. My bad. :-\
It's not particularly intuitive to the modern iOS generation... I was brought up on Fortran, Algol and HTML so can edit the code in the "quote"
The trick is to remove any unwanted text from within the [quote and /quote] tags - I can't use the full syntax here or it would treat them as quotes!
8) You can also edit quotes so that you can quote what the originator never said 8)
eg
Steve, I think you are a biking god!
Post by: AshimotoK0 on January 15, 2016, 10:18:24 PM
PHd carbs ' They won't let you down, won't let you down again' ;D ;D ;D
Post by: onethumb on January 15, 2016, 11:35:08 PM
Steve I think you are a biking God.
Post by: SteveD CB500K0 on January 16, 2016, 07:40:51 AM
Read it on a PC.
Sent from my iPhone using Tapatalk
Post by: UK Pete on January 16, 2016, 08:34:22 AM
[/quote]
PhD Carbs? You need a university education to understand them!
8)
[/quote]
(http://www.sherv.net/cm/emo/laughing/rolling.gif) (http://www.sherv.net/)(http://www.sherv.net/cm/emo/laughing/rolling.gif) (http://www.sherv.net/)(http://www.sherv.net/cm/emo/laughing/rolling.gif) (http://www.sherv.net/)
Post by: Rozabikes Tim on January 16, 2016, 10:17:44 AM
Sorry to any girls amongst us!
Post by: ST1100 on January 16, 2016, 11:02:18 AM
Sorry to any girls amongst us!Methinks you're fine as long as you don't name any parts PMS... ;)
...hon' I swear that this stands for Parked Motorcycle Syndrome, really!!... ;D
Post by: MarkCR750 on January 16, 2016, 08:40:42 PM
Hi, I'm thinking of fitting a set of 29mm CR carbs to my 78 cb750,
Can anyone advise me if it's a good idea or not... Cheers
I look into this a couple of years ago before building my CB 750 K6 café racer, so I agree with Bryanj stick with the stock carbs especially if its a standard engine [not tuned]
CR carbs can even cause unreliability for race tuned engines, they are also difficult to ajust in situe.
I finished up putting K&N filters on mine [stock motor] along with re-jetting which took a bit of sorting, but it goes like stink now.... ;D
I put 135's in my k7 carbs, cheap cone filters, new diaphragm in the accelerator pump, needles on middle slots, I expected loads of messing about but it runs great, also a home made 4 into 1 (well a drastically altered piper 4into1 I should say) no flat spots, I was very surprised tbh, might go up to 138's then!, I don't know where the timing is cos it's fitted with an old piranha gizmo, I just built a new she's so now have space to complete the build at last!.
Post by: Greebo on January 17, 2016, 11:31:49 AM
I forgot to mention that I also fitted a electronic ignition [ Dave Silver] & iridium spark plugs.
I would also like to add that when trying to set up the carbs it wasn't easy initially, & with the stock jets it ran like a pig, we tried different main jets & needle settings before we finished up with the set up mentioned previously.
Post by: Greebo on January 17, 2016, 11:37:00 AM
MarkCR750
I forgot to mention that I also fitted a electronic ignition [ Dave Silver] & iridium spark plugs.
I would also like to add that when trying to set up the carbs it wasn't easy initially, & with the stock jets it ran like a pig, we tried different main jets & needle settings before we finished up with the set up mentioned previously.
PS... when we tried the needle on the middle slot it was still lacking fuel ,even with the 138 jets,so we gradually moved it down & to get the correct fuelling the needle finished up on the bottom slot
Post by: onethumb on January 17, 2016, 11:53:30 AM
MarkCR750
I forgot to mention that I also fitted a electronic ignition [ Dave Silver] & iridium spark plugs.
I would also like to add that when trying to set up the carbs it wasn't easy initially, & with the stock jets it ran like a pig, we tried different main jets & needle settings before we finished up with the set up mentioned previously.
PS... when we tried the needle on the middle slot it was still lacking fuel ,even with the 138 jets,so
we gradually moved it down & to get the correct fuelling the needle finished up on the bottom slot
Hi Greebo and Mark CR750 do you think the 138 jets would be OK on my PD carbs I've read somewhere on the USA site about using 110 jets when fitting cone filters to pd carbs, anyone tried this size and what was the outcome?
Post by: Greebo on January 17, 2016, 12:14:52 PM
Its trial and error mate, it took us a few weeks of trying different jets & needle positions before we cracked it.
I have 4 into 2 open pipes bought from CycleX USA & K&N pods, our main issue at first with the stock jets & stock needle position was the bike wasn't getting enough fuel, when we finished up with the 138 main jet it was still lacking fuel from 2000rpm, it was like riding a kangaroo , so we then concentrated on the needle position, it was only when we dropped it on to the last notch that it solved the fuelling problem, all we had to then was set the air / fuel mixture.
Don't forget that the main jet only really comes into its own on full or near full throttle.
Post by: bladeboy on January 17, 2016, 08:34:14 PM
Post by: westfieldandy on March 06, 2016, 01:00:23 PM
If the bike were to be used for touring long distance and in all weathers then I would probably point you back towards standard carbs because they work better with air filters. and CR's have open bellmouths, so road grime and dirt dont agree with your engine.
Post by: onethumb on March 07, 2016, 08:37:45 AM
I've got the f2 with the pd carbs.
Sent from my iPhone using Tapatalk
Post by: Greebo on March 10, 2016, 10:57:22 AM
I am not really sure how your carbs differ from mine ,ive not had my honda that long so I am not an expert , with mine you have to remove the carbs, obviously, take the tops off each carb to get to needles,its a fiddly job, the guy who built my bike did all this while I watched & Learned, we had the carbs on & off about 5 times before we got everything right.
have you tried searching youtube for info.
Lets us all know how you go on
Cheers
Greebo
Post by: Johnwebley on March 10, 2016, 12:30:31 PM
try this video,
https://www.youtube.com/watch?v=nMFxF-DAJmQ
I recently re-built my CB500 carbs,and to do the needles only needed the top caps removed,
Post by: yozzer74 on March 10, 2016, 03:04:46 PM
Post by: Greebo on March 11, 2016, 10:27:16 AM
Hi, I'm thinking of fitting a set of 29mm CR carbs to my 78 cb750,
Can anyone advise me if it's a good idea or not... Cheers
I look into this a couple of years ago before building my CB 750 K6 café racer, so I agree with Bryanj stick with the stock carbs especially if its a standard engine [not tuned]
CR carbs can even cause unreliability for race tuned engines, they are also difficult to ajust in situe.
I finished up putting K&N filters on mine [stock motor] along with re-jetting which took a bit of sorting, but it goes like stink now.... ;D
I put 135's in my k7 carbs, cheap cone filters, new diaphragm in the accelerator pump, needles on middle slots, I expected loads of messing about but it runs great, also a home made 4 into 1 (well a drastically altered piper 4into1 I should say) no flat spots, I was very surprised tbh, might go up to 138's then!, I don't know where the timing is cos it's fitted with an old piranha gizmo, I just built a new she's so now have space to complete the build at last!.
Mark
where did you get the New Diaphragm from ?, also sent the question in a personal post
cheers
Greebo
Post by: MarkCR750 on March 11, 2016, 09:58:58 PM
Post by: MarkCR750 on March 11, 2016, 10:10:37 PM
Post by: MarkCR750 on March 11, 2016, 10:18:20 PM
Post by: Greebo on March 11, 2016, 11:05:50 PM
Just found the receipt in my emails, a German seller, it was £25, put the item number into eBay but nothing came up, so he must not be selling them now so cruzinimage is probably your best bet price wise.
Thanks,
I Did a search on cruzinimage / ebay , it seems they only have them for 1979 onwards,
so not sure if that will fit my 1977.
http://stores.ebay.co.uk/cruzinimage-uk1484/HONDA-/_i.html?_nkw=cb+750+accelerator+pump+diaphragm+&_cqr=true&_fsub=5561370015&_nkwusc=cb+750+accelerator+pump+diaphram&_sasi=1&_sid=1126387285&_rdc=1
Post by: MarkCR750 on March 12, 2016, 01:32:14 PM
Post by: Greebo on March 12, 2016, 03:02:30 PM
I would have thought Dave Silvers would stock them, but according to the guy who built the bike they don't, I am not desperate just yet as the bike is starting up OK & I have checked the carbs with the filters off & the pump seems to be working, but not tried it on the road yet.
if anybody else know where to get hold of these accelerator pump diaphragms please pop-it on here..my bike is a 1977 CB 750.
Post by: MarkCR750 on March 12, 2016, 04:42:50 PM
Post by: Rob54 on April 12, 2016, 12:28:18 PM
Thanks Mark
I would have thought Dave Silvers would stock them, but according to the guy who built the bike they don't, I am not desperate just yet as the bike is starting up OK & I have checked the carbs with the filters off & the pump seems to be working, but not tried it on the road yet.
if anybody else know where to get hold of these accelerator pump diaphragms please pop-it on here..my bike is a 1977 CB 750.
Hello Greebo,
If you are still looking for the accelerator pump diaphragm they have them on CMSNL here:
http://www.cmsnl.com/honda-cb750k7-four-england_model14390/diaph-set-pump-rubberspring_16021mc9771p/#.VwzZLTGrHEY
They are €17.00, that's about £13.55 at the current exchange rate.
I think you will find that the unit for the '79 model is different as it had CV carbs, it looks to be different from the fische I have looked at anyway. The 'Micky Mouse ears' appear to be positioned differently.
All the Best,
Rob54.
Post by: Greebo on April 13, 2016, 12:41:47 PM
Thanks for the link, very use full.
I have had the old one out & it looks & seems OK Now, but I will hang onto the link & send for one just in case, it does state in their advert they are for the K7
PS.,. I have been informed that these things all look the same but the rod on some of them is longer.
Cheers
Greebo