Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Laverda Dave on July 27, 2017, 05:45:20 PM
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I know this may have been asked a million times before but after searching the carb threads I cannot find the answer I need. Here goes..... Does anyone know of position of the carb needles, Mr Haynes advises the third grove, I've done this but the bike is still a pig to start. I've got the carbs off for the third time now and going through them again. History is they were stripped, ultrasonically cleaned, vapour blasted, new jets, gaskets, needles etc (Keyser kit) and carefully re-assembled. I even made a custom 21mm float height gauge as advised by Chris :). To-date I have started the bike 3 times and every time its a nightmare, it just doesn't want to run, three of the headers have begun to yellow just through trying to set the carbs up, I haven't been on the road yet! The exhaust is a DS item and I'm aware of the potential for more fun and games regarding the back pressure >:(
I'm going back to basics now, stripping the carbs again and using some carb cleaner to flush them out.
Any help or advice appreciated at this stage, I just want to get it MOT'd before winter!
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With an aftermarket exhaust, it will almost certainly not run properly on standard jets/ needle settings. Are you running stock airbox/ filter? What make is the exhaust?
Sent from my X6pro using Tapatalk
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Mine are set on groove 3, original exhaust, stock air box etc.
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Thanks Julie. Hairy, It's a DS item and everything else is stock.
I've just reset the floats again at 21mm and blown everything out. I've lapped the valves using solvol.
I'll try and set in up in the morning, lucky I'm on a week's holiday :)
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It may be worth you talking to Paul Gledhill. He has a DSS exhaust and had a load of trouble getting the bike running right but, I know he did resolve it.......but I don't know how :-[
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It may be worth you talking to Paul Gledhill. He has a DSS exhaust and had a load of trouble getting the bike running right but, I know he did resolve it.......but I don't know how :-[
😬😬 Laverda PM me and I will let you have my mobile number.
It would take ages to do it on the forum.
Mine was the same running weak and would not Rev.
If you have changed the valves and they are not genuine then the 21mm may not be the correct setting. I suppose it depends on the springs in the needle valves.
I also ended up doing the settings with the carbs on their side so the pressure was taken of the valves.
Regards,
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OK Paul, I'll PM you tomorrow, I'm sure you'll have the answers ;).
I've set the floats with the carbs on their side, letting them soak a bit tonight with some carb cleaner in the drillings just in case. I'm going to re-check the ignition again in case its slipped (its a brand new Boyer). I'll put the carbs back on tomorrow after I've err....... taken the Morini :o for its MOT and collected the respoked wheels for the CB250RS rebuild.
Dave
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Hi Paul,
I haven't forgotten :o. I thought I'd get the carbs back on before I PM you. I re-assembled them (how many times now...... ::) ) after checking the float heights again, 21mm spot on, I checked them again the next day, still 21mm, they hadn't shrunk overnight and I put them back on. I rigged up the fuel line and...................they pissed petrol out of three of the overflow pipes >:(. At that low point I turned my attention to the CB250RS rebuild.
I've just got home from work and will go into the man cave this evening to take them off again and have another go, I'll PM you when its something positive and I've hidden the box of matches.............
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I'm sure you have checked but are all the O rings fitting as they should do?. The reason I ask is that I know someone who had their carbs vapour blasted and because it takes off the surface of the metal, the O rings didn't fit snug any more.
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Hi Julie, They all appear to be OK, nothing loose or over tight. All the needles, jets, o-rings and gaskets etc are new Keyster items.
My only concern is the fuel inlet valves, I've seen these with Viton seals in the past and mine are just plain steel. I cant see how these form a good seal against the brass seat without letting fuel by. Looking through a magnifying glass the steel needle tip appears to be rough. I tried using autosol to lap the two together to make a better seal but the valve sits so far into the brass seat I cant hold it to spin it!
Keyster must have sold enough of these kits in the past so they can't be that bad unless I have a rouge kit?
I've been in the garage this evening, I've put the carbs back on the bike after another check and careful setting up and will try and start it tomorrow morning and see what happens.
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Do yours not look like this then Dave?
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Yes it does Julie, I have four of those incontinent little swines >:(
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So which part of yours has the steel bit with no O ring?
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The needle itself, the bit with the cone, my old 400/4 had a very small viton seal on the cone and this pressed against the brass seat, no leaks at all. I don't know if they were original (it was a F2 and the first 400 I restored in the mid 80's. I had to sell it straight after due to the mortgage rate going up to 15% at the time!). I thought that's what I'd get in the Keyster kit. I looked at using the old ones from the carbs but they were seriously mangled, the needles had no spring in them at all, they were stuck solid.
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Maybe you have got a dodgy Keyster kit. I have never used that type, I always use the Cruzinimage kits and I have never had any problems at all. Very frustrating for you though.
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Just skimming this thread and I thought valves - clearances, i mean. That causes a 400/4 not to start if they are too LOOSE
On the DSS exhaust- mine was a git to fit and I ended up grinding some of the collets down to get it to bed into the head. All ok now for 2 years- i just need to mark them if i have to take it off again. Cheaper than an OEM and most don't spot the joints.
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This bike is turning into a nightmare! Another long afternoon spent with the carbs apart for the 4th time, floats checked, all correct, O rings all fine, jets not blocked, pilot drillings clear. I put the carbs back on and the problems are now worse then ever! No 1, 3 & 4 leak from the overflow AND also now from the main air inlet into the air chamber!
The worst bike I have ever owned, it's an absolute pig! Never buy a bike in boxes >:(
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Just a thought you mentioned that you are running a Boyer electronic ignotion. I have one on my 500 and that was a pig to start until I replaced the battery. The Boyers are very sensitive to battery voltage maybe that's your issue
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I replaced the valves on my 350/4 and found they were not exactly the same as stock so the floats were touching the roof of the carb inside, so i gradually moved the tang to lower the float height until they shut the fuel off, i then moved the tang a touch more just to give it space for wear, the carbs don't overflow like they were initially, i run a delkevic 4 into one and apart from a little hesitation off of idle when riding she runs lovely the plugs are a nice tan colour, in the winter i will get a couple of colortune adaptors and tweek the pilot side slightly.
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Thanks Kevski for the tip, I'd like to try it but I really think I've got a duff set of fuel valves from Keyster.
I'm going to buy 4 new valves from DS, they are 14 quid each :( and I don't know the make of them either, I do not they are not genuine though. DS sells the Keyster kits for 19 pounds each but I've been down that road before so not buying another kit only to suffer the same problems ::)
I never had this hassle with the dellorto's on both the Morini and the Jota and the Amal's on the Triton were a piece of cake in comparison :-\
I should have bought a rough bike but a runner, at least I could have heard it running and would have known the potential problems, the carbs on this one were in pieces in a box.
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400's are prone to bad starting if down on compression
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When i lapped mine in, i used a cocktail stick with a bit of solvol on it for the seat, and the valve fits nicely in a biro tube which i then lightly polished using a piece of stiff card which i poked a cocktail stick through and a little bit of solvol on the tip of valve and twisted the valve in the hole lightly between thumb and finger like seating an engine valve only takes about a minute.