fueling problems

[peteb]

hi im just starting to find my way round the site and have posted this plea for help some where else but i think it should be here so here goes again.I have just finished restoring a 400/4 and would love to enjoy riding it but i cannot get it to run properly.

from cold it starts easily and ticks over fairly well .when its warm if you crack the throttle open sharply the engine wants to die,if you open the throttle gently it will rev ok. it is not nice to ride in traffic as at low revs it seems a little gutless.

Ihave had the carbs ultrasonicly cleaned,fitted new jets etc,checked float heights,tried different neadle positions all the usual things

It does run better on half to three quater choke so would suggest weak mixture but the plugs look a little rich .

I have also fitted new coils,cam chain and tried timing as per book and alittle more reterded but nothing seems to make much difference.

In 40 years of fiddiling with things mechanical I dont think ive been so frustrated


HELP PLEASE

[K2-K6]

Hello and welcome to the site hopefully someone here will be able to put their finger on something to help you get it going better.

Sounds as if you have reasonable confidence in the carbs.

I always find that retarding timing prevents any revs increase so would try it with a swing the other way to see what happens. If so you'd possibly suspect the advance/retard method as being stuck.

Are you certain about the cam timing? as this can run you in rings even if one tooth out.

Have you got any compression readings for each cylinder to verify general mechanical health.

[Bryanj]

A bad or not fully charged battery can do this especialy if the regulator is sticking, also wrong grade plugs--they SHOULD NOT have an "R" in the designation no mater what the NGK book says

[peteb]

hi thanks to you both for the replies,iforgot to say the bike is fitted with boyer ignition and seems to advance ok when checked with timing light ,battery is new but may be suspect as it wont turn the bike over so i will try to jump it from a good one tonight .as regards the cam i have replaced this with a new /second hand one as the original was very worn the only thing i dont know about here is that the original cam was marked as 360 and the replacement 359 but looked the same and i could not find any info on the relevance of the numbers.I have checked the compression but only on the kickstart an it read the same on all 4 pots at about 130 psi.When i had the head off it looks like it has had a rebore to .75 over size fairly recently but i will check compression again on the starter motor with a jumped battery as the book gives a figure of 170 psi but i assumed the lower reading was because i was only kicking it over.

perseverance furthers

thanks again and i will let you know how i get on.  pete

[peteb]

hi, spent a while up the shed last night and have made some progress. I set the timing again but this time at 2500rpm and set it to the fully advanced marks which has made a huge difference.Iwill check the charging curcuit tonight and swap the battery from the old XBR500 which Iknow to be good and see if this irons out the last little bit of hesitation that remains when you crack the throttle open.


thanks again for your help

ps does any one arrange meets in the south east

Pete

[K2-K6]

Sounds good, at least you should be able to get more of productive run out on it to fine tune a few things.

If it still seems lean you could try it with the needles pulled up (circlips down) one notch to find if it improves or not.

Plugs would normally be NGK 8 grade I think.

You should be running at about 14.0 volts when charging flat out (about 2000rpm upwards) to be healthy.

There was some discussion of an informal meet-up at Box hill this summer so we'll have to round up a few that are near to meet a few of us.

Where about in Sussex are you?

[peteb]

hi sorry i have not got back on here sooner. bike seems to be running pretty well now so lets hope we get some decent weather soon.

im in a place called Hurstpierpoint just north of brighton so box hill would be good.

i will try to get a photo of the bike up soon

cheers pete

[Boggieman]

Hi All

Apologies for slightly hijacking this thread, but if you do not recommend the NGK 'R' plugs, which ones should be used. Only I am currently having problems with my 400/4, as it will not fire on the Number 1 cylinder. I have a good spark from the plug, the cap is good, and the other thre cylinders fire just fine.
Would this point you in the direction of the carb', maybe a needle dropped or float sticking?
Any help would be gratefully received.

Ian

[470four]

Hi All

Apologies for slightly hijacking this thread, but if you do not recommend the NGK 'R' plugs, which ones should be used. Only I am currently having problems with my 400/4, as it will not fire on the Number 1 cylinder. I have a good spark from the plug, the cap is good, and the other thre cylinders fire just fine.
Would this point you in the direction of the carb', maybe a needle dropped or float sticking?
Any help would be gratefully received.

Ian

Hi Ian

Standard plugs are D8EA NGK, or DR8EIX Iridium     Got Iridiums in mine, no problems...

Would assume yes - carbs problems, fuel flow related? You have good flow out of the carb with fuel supplied and the float bowl off? Mains & pilot jets clear? Is number 1 exhaust staying cold on tickover AND part-throttle??

[Boggieman]

470four

Thanks for that, will look into getting some D8EA's. Exhaust on No.1 gets warm but the others get so hot you cannot bear your hand on them.
Plenty of fuel is going to the carb, and the plug is wet when we removed it, but when we blocked off the air intake to the carb' there was no appreciable difference. Possible air leak on inlet manifold???

Appreciate all your help
Ian

[470four]

470four

Thanks for that, will look into getting some D8EA's. Exhaust on No.1 gets warm but the others get so hot you cannot bear your hand on them.
Plenty of fuel is going to the carb, and the plug is wet when we removed it, but when we blocked off the air intake to the carb' there was no appreciable difference. Possible air leak on inlet manifold???

Appreciate all your help
Ian

Ian
400/4 manifolds will go hard after all these years and then suffer an Epic bond failure between the alloy insert and the rubber itself:



 



The screws holding them on are an absolute arse to get to - forget getting an impact driver in their, no room.... I settled for chiseling off the top of the alloy insert then twisting the manifolds out, with the pressure released the screws came out easy enough with mole grips on them?

The manifolds & O-rings are still available from David Silver, use allen bolts to refix  

The middle two will get cooked first, directly behind the block & running v.warm - wouldnt hurt to replace them anyway...

[Boggieman]

470four

Thanks for that. I am hoping to get new plugs today and will try them first before attempting to get the bank of carb's off. It does look like the manifold rubbers have been off before as they are held in with Allen headed bolts .
As I said before, really appreciate all the help.

Ian

[K2-K6]

Assuming you've got sparks at the right time and fuel on the plug then you'd have to consider the compression.

What do the cylinders measure when tested?

Have you swapped #1 plug with one of the others to see if the problem switches over?

The pipe will heat up just a little even if not firing, but after about 1 minute they would usually be too hot to touch.

[Boggieman]

K2-K6

Checked the compression last night, starting at No1 pot it goes 80psi, 75psi, 75psi, 80psi across the engine. Yes have swapped the plugs from 1 and 4, problem stays on No1 pot. Dismantled the carb' for No1 last night and apart from a tiny constriction in the main jet it was really quite clean, haven't had chance to get them back on the bike to try them again yet. All inlet rubbers were in a good condition, all still quite flexible, not gone hard and broken ( I think they were newish when I picked the bike up).

Was wondering though whether the plug lead could be breaking down, and only manifests itself when connected to the plug, ie; when disconnected all appears well Realise this sounds like I'm grasping at straws, but I am getting to that stage.

Thanks for all the suggestions.
Ian

[K2-K6]

You can also switch the leads of 1+4 over to check that as they are fired from one coil (may have to unbolt the coil to do this but make sure you still have a good earth).

Make sure carbs are full then take tank off and start the bike in as near dark conditions as you can manage, you'll be able to see if the the leads are leaking and sparking across to any metal parts near them.