Aye, weak or no return spring, or too much advance caused mine to take a while to return to idle.

Edited 22 August, 201214 yr by MaxGT

Well she shat herself earlier, dumping all the coolant on the deck. I heard a bit of a pop, thinking it was a backfire turned to look to find the thermostat housing had split around one of the hose take offs, blowing the pipe clean off, with take off still wedged inside the rubber hose Of all the places to split (considering some areas have been plastic welded), I can't fathom why it was here. Luckily my head wasn't under the bonnet or else I would have had a face full of boiling coolant. Fuck sticks. Quick trip to the scrappy (where I knew they'd be a 6n!) and I got myself a replacement. By the time I got home and had prepared the 'stat it was pissing with rain and I'd lost the motivation. Seriously, if it can go wrong on this car, it has! And there I was thinking I was going to get an MOT this week

Edited 22 August, 201214 yr by prankstar2003

Unlucky mate.

Also if your throttle cable isn't really free it'll take time to come to idle

Fix the leak and get it to an MOT simon, stop being a whiney bitch!

Leak? The pipe take off blew straight off! Anyhow I've replaced the thermostat but it sti wouldn't work. Thought it might be moisture on the leads/plugs etc so whipped them out to find they were all loose in the head. They were tight in yday, but I'd done it when the head was hot so I can only guess they'd loosened off as it cooled. Plug 3 wouldn't tighten up Somi decided to take it out only the find the threaded part of the plug had snapped away from the rest, leaving the thread in the head! Eazi out sorted that and luckily I had a spare set of plugs. Still wouldn't run. Saw one of my earths getting really hot so replaced that and she ran! Wehey! Also made a paper gasket as I think I may have had a small air leak on cyl. 2.

Max, I'm too scared to take it anywhere as even the slightest bit of load tends to make it stutter. I'm hoping it's been this earth all along as it was getting red hot, we shall find out tomorrow, if I can get an mot booked

Well this fucker still won't run. When I left it Thursday it was running fine and would start ok. Gone to try it today and it won't start without me changing the timing. Reversed it off the drive and drove back on and it dies. The running had gotten worse since its test run a few weeks ago and I'm out of ideas why. There's fuel and a spark, but it won't fire. When it does I need to mess with the timing to get it smooth. I'm going to change the plugs and leads as a last resort. I'm totally out of ideas

You're positive the timing is actually any where near correct?

How big is the spark? It should be nice and fat.

The choke working ok?

I'm not using the choke. Most people seem to be ok without them. Timing was set to around +5 when it was running ok. Spark looks ok, kind of hard to see it in this light. Thing is it will run, but then not fire up again once it's stalled/dead

Maybe I'll try using the choke, if I can find the sliding plate from the carbs

Edited 26 August, 201214 yr by prankstar2003

Bike carbs preety much need choke on cold start up mate . pig to start with out :/

Don't forget every engine is different, and at a different spec, it all depends on the current tune of the carbs too.

Some people might be using bigger idle jets, or have the mixture screws set differently, which will mean cold starting will be much easier.

Aha, I have changed the idle screws actually, I wonder if that may have something to do with it. That was only very recently though, even before it wouldn't start nicely.

I'll try the choke

I'm not very familiar with the bike carbs idle circuit,

But its not gonna want to start if its jetted quite lean on the idle side, the fuel will just be puddling on the inlet manifold walls, and dripping into the cylinder at best,

It it coughing into life at all or is it just completely dead?

Also, have you adjusted the mixture screws at all?

should be the case of 3 screws out . Screws controll low throttle and idle

Coughs now and then, but mostly dead. The mixture screws (next to, not in the float bowls right) are 2.5 turns out

Pull them another turn out and try again.

Choke appeared to make no difference, but it's on there now, so I'll leave it. Mixture screws another turn out and she's now running. Little lumpy, but maintaining a nice 900 idle. Just waiting for the inevitable cough and splutter

Right.

You timing to the right mark? If not you'll be 6 degrees off to begin with? Saying that you don't have a timing belt cover do you?

Idle screws I'd go 2.5 turns out from stops.

Ignition base timing 8-10 degrees, or 5 with vac advanced.

What main jets do you have again?

Mine literally would not start without choke before, only just about does now on hot days, it isn't just there for banter, bikes are setup properly from factory and they feel the need to fit a choke

No timing belt cover no. I'm timing based upon a square part on the oil seal plate. I'm 99% sure this is the correct timing mark.

Tried 2.5 turns out nick and it was shit. I've now gone 3.5 and it seems ok. I haven't felt the need for a choke since its been starting fine without it up until now. Choke is fitted anyhow, so we'll see. Jets have been drilled out to around 160. I did this myself so I can't be 100% accurate

She ran up to temperature there no problems (she stalled the other day when idling on the drive after a while). Also took the revs up and snapped the throttle closed. Again, all well where she would have stalled before. So now I feel I'm where I was a few weeks back.

I'm not convinced by drilled jets tbh.

Breathers free?

Tried everything suggested now and still no luck. Really considering fucking this engine off and starting again.

It doesn't seem to be running as hot now, but under load, it struggles when warm. Once you hit what under load, as the revs come down, it just stalls. Does start up easier than it used compared to when this started.

When I put my hand over the carbs, the engine tried to die. The exception is carb 2. When I put my hand over this one, the revs actually go up a little. Why?

You actually conducted any health checks on engine?

Tbh, I would:

Compression test

Leakage test

Set plug gaps

Remove carbs

Blow on the fuel inlet; then turn them upsidedown, that should stop you being able to blow

Disconnect any pipes off the carbs except the fuel one

Ensure all 4 slides slide up and return smoothly and at an equal rate

Ensure inlet manifold is sealed to head properly

Ensure your joining rubbers are sealing ok

Oh and try some jets which haven't been drilled? I guess you used a 1.5mm and assume the slight movement makes them about 1.6?

I have done some of that yeah. Plugs were brand new, can I not assume they are set ok?

Would these problems cause it to die when under load though? So pissed off with this. Week spent trying to sort it and I'm going fucking backwards

Just chill out dude, you need to put a bit more effort into actually eliminating the different causes that are giving you there symptoms,

The first thing i'd be doing is checking for air leaks, get it running, and then spray either WD40 or carburetor cleaner on every possible joint/orifice that could be open to atmosphere and letting air leak into the inlet tract un-metered. I prefer to use something like carburetor cleaner as it doesn't leave an oil residue on your nice clean components.

Once your 100% sure there are no air leaks, then cross that off the list. By the way, when i say "the first thing i'd do" this is after making sure the engine is showing adequate compression across the 4 cylinders, as any problems here will cause you problems, and its not un-usual for novice rebuilt engines to show a lack of compression on a number of cylinders. Also, whilst checking for air leaks, make sure there isn't any pipe fittings on the carbs that are supposed to be linked to something, thus causing un-metered air to be dragged in, post venturi.

There's no point in just drilling the main jets up and up, the carbs aren't using these to metre fuel the way your running it, the mains will only come in to play circa 2500RPM+ (correct me if i'm wrong nick, i'm used to webers). The idle jets are what is controlling the fuel mixture, then the mixture screws which aid in fine adjustment of the fuel being metered by the jet. I don't think anyone has had to up the size of these jets, as idle jets tend to be sized against the size of carburetor, not the engine like the main jet(s)

It's not sounding like anything terminal, just sounds like the carbs and ignition system need dialing in properly...

I reckon you should try another hall sender if you can. Just to eliminate it.

IMO 150 jets will be adequate to start and drive it without being too lean.

It's everything else though, we don't know what your carbs are like, they may LOOK ok but could be nackered.

I wasted an entire day trying to get mine to work as I'd put the float bowl breather onto the return fuel line, that slight restriction made it so rich it would barely run.

Is your cam timing even right? How did you set it with the GT cam?

I'd conduct a hot and cold compression and leakage test too.

Ignition it will run and rev up and drive between 6-10 degrees advanced tbh.

Air screws don't have a huge effect only at idle tbh.

Are your needles adjustable? What position are they in? Are they all equal?

You can barely feel any auction on any of my carbs, so I think you really need to concentrate on cylinder 2 here, will suck more if the butterfly is open more, have you actually took the carbs off and compared the butterfly resting positions?