1st Start on rebuilt engine.

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Rebuilt the engine from the bottom up.
New standard big end shells, rebored to +20, new pistons and rings, tri spark, new valves and springs. New premier carbs.
It starts and runs well with full choke, the moment I take the choke off it dies. It does not want to respond to the throttle.
Needle is set on the middle slot and assume I should go to the next slot down the needle to richen the mixture. The plugs are light brown with a cream coloured end, exhaust pipes look hot blueing the chrome, only static timed it, not fitted the air filter yet for obvious reasons, I know this will richen the mixture.
 
Unfortunately a lot of the Premiers have been shipped with swarf in the pilot circuit. you would be advised to remove and clean them out completely before starting to make any other changes.

Cheers,

cliffa.
 
My new Premiers had the nasty swarf in both of them. Found that out after installing them and they exhibited the same symptoms as yours. Off they came and a thorough cleanout including guitar string probing. Worked great after that. 6 months later off they came and a single Mikuni VM 34 went on. I've never gone back.
 
Many thanks for the information, I will be tightening the head in the morning so will give them a good look over.
 
Oh, and welcome to Access Norton Ratboiler.

Cheers,

cliffa.
 
Congratulations on getting the engine built. If the pilot jet cleaning doesn’t fully solve the problem recheck your float levels. If they are too low it will run lean and heat up the pipes. I had the same problem with my recent rebuild. For some reason it wanted the air slides down a bit until about two hundred miles into the break in it just cleared up and now runs well. Not a scientific analysis I’m sorry. Best of luck.
 
Many thanks for the information and the welcome, I have been on this site reading for a while.
I see Matt from CnW is well thought of on this forum which I can confirm having bought some very well engineered parts from him.
 
Rebuilt the engine from the bottom up.
New standard big end shells, rebored to +20, new pistons and rings, tri spark, new valves and springs. New premier carbs.
It starts and runs well with full choke, the moment I take the choke off it dies. It does not want to respond to the throttle.
Needle is set on the middle slot and assume I should go to the next slot down the needle to richen the mixture. The plugs are light brown with a cream coloured end, exhaust pipes look hot blueing the chrome, only static timed it, not fitted the air filter yet for obvious reasons, I know this will richen the mixture.
Hi , without knowing how familiar you are with Amal carbs I will ask the obvious. Can you confirm that you are taking the choke off and not applying the choke. This would not be the first time that this has happened .As you have not yet fitted the air filter it is easy to look in the throat of carb and to open the throttle and check that it works .
 
Hi yes the choke is on when the cable is slack.
It will run with choke on(slack cable) very well, but the slightest movement to choke off kills the engine, or if I twist the throttle it will backfire and not want to respond.
I set them up to the book, and checked the jet sizes which are all stock.
I had the pilot jets out today to check for any sort of blockage and all is clear.
Next to check is the floats as the bike seems to be starved of fuel. All filters checked and ok, checked the tank and when I did run the engine I had both fuel taps on.
I did notice that once the engine was ready to go the tickler once depressed took around 5 seconds to flood. Other bikes I have had flood almost immediately.
So i have ordered a kit for checking the float heights as scout63 advised.
Tightened the head down today after running the engine yesterday and most bolts and nuts needed it.
Watch this space
 
Hi yes the choke is on when the cable is slack.
It will run with choke on(slack cable) very well, but the slightest movement to choke off kills the engine, or if I twist the throttle it will backfire and not want to respond.
I set them up to the book, and checked the jet sizes which are all stock.
I had the pilot jets out today to check for any sort of blockage and all is clear.
Next to check is the floats as the bike seems to be starved of fuel. All filters checked and ok, checked the tank and when I did run the engine I had both fuel taps on.
I did notice that once the engine was ready to go the tickler once depressed took around 5 seconds to flood. Other bikes I have had flood almost immediately.
So i have ordered a kit for checking the float heights as scout63 advised.
Tightened the head down today after running the engine yesterday and most bolts and nuts needed it.
Watch this space
Hi Ratboiler, Did you take the carbs off and clean them? The swarf in mine only came out when I had them on the bench on their side, and was a very thin tubular shaving. No amount of poking around would have removed it.

Cheers,

cliffa.
 
I really hope you don't have to do it on a new set of carbs and it's a last resort but you may end up digging the Welch plugs out of the mixing chamber to see if there's any debris in there
Cheers
 
You say it 'runs well with full choke' Is that idles well?, or will it rev with the choke full on too? Have you checked fuel flow from the petrol pipes with taps open? It shouldn't need two to run...
 
What year and model bike? Sounds lean. Checking the fuel level in the float bowl is a good start.
Assuming you set the mixture screws at the standard one and a half turns, try turning them half a turn in to richen the mixture. What pilot jet did your carbs come with. If they are 17's you may have to go to 19's.
If that doesn't help try raising the needle by putting it in the lowest groove.
Try to get a timing light on it as soon as possilbe.
 
Thanks for all your advice yes the carbs are off and on the bench. I had the pilot jets out and checked, even sprayed WD40 into the jet housing and saw it rising out of the carb on both so clear there. Getting expert at taking them off now.
Estuaryboy yes it runs and ticks over well on full choke, but will not respond to opening the throttle, it then backfires and plays up. Plug colour when removed was light brown showing lighter at the end. A slight movement to take off the choke kills the engine. It's a 73 Mk1 all settings as the book as are the jets and needle position which is the middle.
I checked the flow from the tank yesterday which seemed to be ok, the reason for using both taps was to be 100% certain of getting enough fuel, and will remove the tank taps today to check the filters.
 
You keep saying the jets are ‘to the book’... but pilot jet numbering on the Premiers is different to the old pilot jets. So the pilots jets must NOT be to ‘the book’.

Htown already mentioned this, many Premiers have been being supplied with pilot jets that are too small, I believe Burlens are beginning to respond to this, but you need to check what you have. My T120 had very similar symptoms to yours and it was down to having too small pilot jets from Burlens.
 
Hi All,

A mate on a french forum had exactly the same problem as yours, which was solved by cleaning very carefully the pilot circuit as recommended in several posts above. In particular, you must see the liquid used to clean it coming out of the two small orifices (one in front the other behind the slide groove on the engine side of the carb).
And as said by Eddie, a 32 mm carb works better with a # 19 pilot jet from my own experience.

Laurent
 
Many thanks once again for all your comments it makes for interesting reading and nice to know I am not alone trying to sort this. Eddie I will check the pilot jet size and report back. What I meant was I stated the jet sizes to AN and they sent the carbs already jetted. I checked the ones in the carb which were to the book and assumed the pilot would be as required.
Waiting for carb level checker to arrive and let you know how I get on.
 
Hi
Happy Easter to all, wife had me doing all sorts of odd jobs hence my delay in getting back to the bike.
I have checked the pilot jets all ok, and sprayed WD40 through the pilot jet recess to see it coming out of both points in the carb body.
The carb jets are as follows 106 needle jet, 260 main jet, pilot jet RJ17, slide 3.5.
It's an 850 Mk1.
The carb float level kit was out of stock, does anybody know of a way to check the float level? I have the carbs off and on the bench.
 
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