350 4lo cold start difficult tried everything to cure it

[murp]

ok where do i start...... when i brought my lc 10 years ago it had a cold start problem..... it needed lots of fast kicks to get it going..... when warm or hot no problems...

over the past 10 years it has had new plugs...... banshee coils...... pulser and high/low speed coils checked..... carbs been off numerous times for cleaning, float bowls correct, float valves not leaking..... i think i've tried most things

but i'm thinking maybe the cdi is not providing a strong enough spark..... the capacitor which stores the charge in the cdi is nearly 40 years old, and capacitors degrade in time

could this finally be the culprit..... has anyone else changed cdi to cure bad cold start....... is there any way to test the cdi unit, its producing a spark, but would a weak spark be a symptom of bad cold start....

finally would a zeeltronic rd07 used on its own produce a stronger spark than a 38 year old yamaha cdi....

i'm 60 years old, and this cold start problem, which used to be just a nuisance is much more difficult to live with as i get older.....

cheers all

[murp]

could I try a different heat range spark plug to prove a weak spark.... if so what plug would I go for.... I'm running b8es plugs at the moment.... cheers

[shaunthe2nd]

I've had 2 similar problems.
One i cured by stripping carbs, full ultrasonic clean, including choke etc and replacing and that sorted the starting.
Another turned out to be a slight leak on the head gasket, which when changed sorted the problem.
I guess it can be a multitude of things, and helps to find out what it is one step at a time.
Good luck with it.

[oldbritguy]

Hi Murp

If you look back through the threads in both this and the advice sections, you will see this is a fairly common theme which pops up every now and then.

Quite a difficult problem to diagnose from the other end of the internet as your issue might be simple or totally different from many of the others which have been brought up here.

I would start simple as you suggest and check for a spark with a new plug (B8s are spot on)when the bike is cold. Plug on lead held against head and kick engine over with ignition on. Disconnect other side also to save you getting a belt should engine fire. A decent spark should in theory eliminate any CDI problem as a cold issue.
Look at the condition of all the rubber connections between carbs (black hose between them on fully and tight and no hardness or perishing) and also the rubber reedblocks including the balance pipe. No cracks or loose connections here as this would result in a weak mix due to air leaking in making cold starting difficult.

As Shaun says, clean the carbs thoroughly. Ultrasonic and balls out to clean the pilot circuit. Don't forget the air filter.

If the bike has been sitting any length of time then the crank seals might need replacing which will also cause difficulties starting and running. Do you have access to kit for a leak down test.

As stated, could be any of the above or something else completely different.

You don't say where you are located as maybe another forum member who is nearby could assist swapping some things over to try and eliminate some of your suspicions.

Hope this helps (or have I just muddied the water?)

John

[murp]

john

thanks for taking the time to reply...... i'm in grays,essex

the carbs have been off many times, emulsion tubes removed and cleaned...... the test i did for float valves was i let it run till it stops with fuel tap off..... the next day i try to start it, same problem, so float valves cant be leaking..... float height is spot on.....

but i must confess ive not had the brass balls out, but im sure ive checked the jet behind the balls sometime in the past, but cant remember now how i would have done that....

ive had the balls out on my rd400c and replaced them with grub screws

surely the jets behind the balls are checkable without removing the balls, but cant remember how i did it.

once i have it started , if i stop the engine and restart immediately it starts ok , even though its not warm

i will re check ohm readings across all coils again and post the results on here later....

thanks everybody

dave

[Tobyjugs]

Have you tried measuring the compression?

[murp]

yep compression is ok.... or was when I did it some time ago

[LC_BOTT]

Just another suggestion, as not sure if it would make a huge difference. Are you running resistor plugs and resistor caps? and not sure from your post whether you've had the pilot jets out and cleaned. You might need to go up or down a size here as well.

[murp]

b8es non resistor plugs and black non resistor caps
pilot jets standard 22.5 clean..... as said earlier not had the balls out though

[shaunthe2nd]

Definitely worth taking the balls out and cleaning behind, several of us have had some great performance improvements after doing this.

[murp]

it runs so well once it's started, it's only cold start that's the problem.... Will brass balls have effect on cold start only..... but that is the next thing to try I suppose...... this bike has had this problem since I've owned it (10years).... I've done loads to try to cure it, but just lived with it.

cheers

[Tobyjugs]

I would also play with the pilot jets . Deliberately making it lean or rich to see if it makes any difference, after i knew the carbs were in tip top condition.

[steven]

Hi John,

Do you know the history of the bike before you got it 10 years ago ? ie, when last did it have any TLC before you got it ?
How many miles are on the clock ? has it ever ran right for the ten years you have had it ?
Id start at the begining, with a compresson test and a pressure/vacuum leak down test, then take it from there.

I dont beleive you can check the jets behind the brass balls WITHOUT taking them out.
Almost 40 year old CDI,s etc cant be helping either, substituting one with a know good one would be one way of ruleing that out.

If you cant be arsed doing a press/vac test, one crude way of doing a test is, to get a can of easy start from Halfords and with the engine running, spray it around the engine at any possible place where it could be drawing in air.

It might have a pressure leak, or it might have a vaccum leak, or it might have both, if it has a vaccum leak, it will draw the easy start in, and you will hear the engine RPM rise, if it has a pressure leak, you might not know using the easy start method, as it will just blow the easy start away rather than drawing it in. I,v never had it, but I have heard of some engines that will hold a pressure but not a vaccum, or vice versa. The correct method is to check BOTH.
As we know, a 2 stroke engine has to hold both a negative and a posative pressure inside, so a correct leak down test should include a pressure AND a vaccum test.
Please keep us posted how you get on.
Regards,
Steven.

[wallcraft]

Sounds like crank seals to me, not the same lump but I had the same problem on a CR250. Change the seals and bingo , sorted.

[midlifecrisisrd]

4 things you MUST do

Whip your balls out. If you have done it before you know it is not a big job - just to rule it out.

Check your float heights. From the cut out on the carb body, not the gasket.

Check the fuel tap isn't passing. Take the fuel pipes off and fit some spare tubing to the tap and into a glass jar. Ideally keep the lid on but pop neat holes in it for the tube to go through. This will stop it evaporating as fast as it weeps if really slow. Leave for a few days. Float valves can pass very slowly.

Do a leak down test. The carbs are off anyway so just the exhausts to come off. Leaks can stop as the engine heats and rubber seals soften. I've had 2 bikes that ran fine (one was a bitch to start) but if the fuel was left on it would flood the crankcase and p1ss out the left seal.

Steve

[midlifecrisisrd]

Just had another thought on this

It does sound like the choke isn't working

Next time while it's cold take the balance pipe off and add a few drops of petrol in the holes and refit the tube

Then try and see if it fires any better

Steve

[murp]

thanks for all the info chaps...... lots to check..
.

just done some resistance measurements

red/white to black 88.7 ohms
red to brown 5.2
brown to black 234

banshee Orange coil
primary 0.4 ohms
secondary 10.3kohms.... this is way above 3.5kohms specified, but they are not standard coils.... thoughts please...

cheers

[midlifecrisisrd]

As they are not standard it is not applicable

If both coils measure the same then I would take them as good

Steve

[ringding]

Can't see it mentioned above but seeing as how I've made this mistake in the past thought I'd suggest...
Is the joining pipe between the two carbs in place, the one that runs horizontally between the two carb bodies? My recollection is that it was a bitch to start with out that. I did manage it but fortunately realised my error before riding it.

[muttsnuts]

take your carbs off and send me a photo of each under side of each carb and also the float bowls, its could be the float bowls are on the wrong carb or the choke pickup tube is missing/broken

if they are ok, then check that your timing is correct and that you have a woodruff key holding the flywheel in the correct position, you'd be surprised how many bikes I get in with the key missing !

Also verify your compression figures, if either are below 100 psi then you will have issues, ideally you want 110psi or above

[murp]

this is the choke side carb.... just got the brass ball out... jet was clear but a load of crud in orifice.... don't know if it was blocking hole in carb body though

[murp]

mutts.... I can't get to other side of bike yet.... if you need any more pics of choke side carb let me know....

cheers all

[murp]

I may need a couple of new o rings..... any idea of the size..... also 2 brass balls.... I don't think the orifice has enough meat around it to tap and use grub screws like i did on my 400

[steeley]

Hi , it looks like you have ledar emulsion tubes fitted . Are you running foam filters or std airbox .

[murp]

Steeley.... standard airbox..I didn't know they were non standard emulsion tubes

[muttsnuts]

ok, measure the brass tube (middle photo that shows the gasket), the tube is at 12 o clock to the left as you are looking at the picture, that looks too short, it should be 10mm long, also I see the float bowl is number one, which is the non choke side bowl, so you need a number 2 float bowl which is the choke side bowl (has a small jet in it, the brass tube I am referring to goes inside the choke draw tube and feeds the jet) that is your problem

[stusco]

Your the man Mutts

[murp]

I'm doing a little jig for joy shopping with my wife in Morrison's..... by Jove I think you've sussed it mutts thanks so much and everyone else.... I'll try and get other carb off later and check that float bowl..... you don't know how long this has been giving me grief.... May as well get other brass ball out when I get carb off

[ringding]

Nice! I've also made that mistake too! Should of thought to suggest it. Nice one muttsnutts...

[midlifecrisisrd]

Stewards enquiry

Bum steer with the "float bowls correct" comment lol

Steve