My bike rough starts when cold but fine when hot???

[brythered92]

Hi All,

Wondering if anyone can point me in the right direction here please?

So i have a 98 hornet owned her for 3 years now got about 38k on the clocks do most of the basic servicing and rarely do over 1,000 miles per year. It sits under a cover outside all year round. I always seem to come into trouble when i wash it with water (yes i use bucket method with light rinse just to take the soap off no pressure washer or anything).

The latest issue is that the bike seems to want to start but wont when its cold. I have had a new battery about 6/7 months ago and charge it up when it drops due to the cold / infrequent use and use various other batteries to check it have and doesn't seem to make a difference. When i spray carb cleaner into the air intake just behind the left fairing panel it fires up and i give it a slight bit of throttle to get her going and boom she's awake! When the bikes hot i turn it off and starts again no problem.

The choke and throttle both have to be absolute zero to try get it to sound like it wants to start when it's cold. If i try putting a tiny bit of choke or twist the throttle to aid starting it just sounds like its drowning in fuel and boggy and will refuse to try turn over at all. Most of my previous issues were around carbs and similar but have sorted them since and it's been running fine for a good few months. Up until i washed it again a few weeks ago!

Most people point to valve clearances for the hard starting in cold conditions as the most common go to. My nose is pointing more towards weak / no spark not being able to ignite the fuel unless carb cleaner is sprayed into it? Maybe this happened when washing it and has damaged the plugs or let water in to it? I will pull the plugs first to check and keep you updated but just wanted to see if anyone else out there can say this happened to me and it was this etc!

Thanks in advance!
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r6 99 quill pipe ....

[jaffa90]

Usually valve clearances on HOT starting problems.
"""The choke and throttle both have to be absolute zero to try get it to sound like it wants to start when it's cold. If i try putting a tiny bit of choke or twist the throttle to aid starting it just sounds like its drowning in fuel and boggy."""
This is not normal, also twisting the throttle bypasses the choke on some carbs.
Wet H.T. leads can weaken the spark to the plugs. (i use a watering can to rinse).
What is the idle / tick over speed when warm up and what happens when you give it some choke ?

[Tdibs]

Yeah my inclination would be to look at the condition of the HT leads. Twist off the caps and see if you have shiny wiring or corrosion inside.

How do the inlet boots look? tried spraying easy start around those while its running?
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Previous : 09 Vanvan 125| 02' Sv650s || Current: 1999 Xj600n | 1992 DR650 RSE | 2005 Fazer 1000

[MCN]

Spray the electrics with WD-Fuckwit.
It's primarily a Water Displacement compound. (Clue in the name)
If it's HT leakage due to moisture/water the spray should resolve that. Then look at new HT leads andnplug caps while you're at it.
I may be mistaken, I think HT leads are carbon filament as opposed to a copper wire. Both have issues but I always preferred to phaph with copper core.
When did you last check Valve Clearance? 30k is probably about time to CHECK and adjust if too tight.
I don't know if hornet is cam with shim or push rod with adjuster. 🤔 cam and shim is a cnut to do but they seem to last between adjustment longer than push rod type.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Nobby the Bastard]

Value clearances can result on poor starting when cold (it's down to different metals in the head a d valves expanding at different rates resulting in the clearances opening up when hot)

Typically it'll cough and splutter for a couple of minutes and the burst into life when its warmed enough for the clearances to open.

I had this problem on .my fz and it took me weeks to find the cause.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[brythered92]

Thanks for the quick replies.

jaffa90 - Wet H.T. leads can weaken the spark to the plugs. (i use a watering can to rinse). i use a small sports bottle to pour over the tank area.
What is the idle / tick over speed when warm up and what happens when you give it some choke ? Standard just under 1.5 when i give it choke and its warm it revs up a bit like it should i think but ill try again to confirm.

Tdibs[b] - I will check the HT leads and things later today to see if i can work out if its them! Haven't checked inlet boots yet but could possibly be an air leak if thats where you're going? Will check again as had that problem a while back causing it to run rough.

[b]MCN - Thanks for the WD tip haven't done that in a while will give it a going over again. And i believe they are due around 35 i've not checked them in the 3 years i've owned it so wouldn't hurt to check i guess. Think it's cam with shim mate.

Nobby the Bastard - Yeah thats what i read about the expanding when hot which makes sense really. But yeah thats what it does pretty much! guess it's easier to check for the sparks and leads first before taking the cover off and playing with clearances. [/b]
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r6 99 quill pipe ....

[wintelf94]

[Robby]

This is one of the few times that a fuelling problem could actually be fuelling.
If it's hardly ever getting ridden, then the fuel will evaporate and leave a sticky varnish residue. If it only gets short runs when it is ridden, then this crap isn't get washed off with petrol. A fuel stabiliser would help there.

Or course, could also be moisture in the electrics (HT leads or loom connectors). Likely to be a bit of corrosion on the earths and battery terminals as well. Spraying anything electrical with lots of WD40 will help there.

The solution is to ride it more. Heat, vibration and airflow do a wonderful job of keeping things clean and driving out moisture.

[Tankie]

Drain off the carb bowls , to remove any water
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Always learning, everyday is a school day

[brythered92]

So far i have....

- changed battery
- pulled plugs checked gaps etc a slight bit wet but otherwise look good, strong spark.
- sprayed all electrical parts and connectors with WD40
- drained carb bowls
- set up temporary fuel tank so i could see it going into the bike with tank off.
- checked for air leaks

none of this works so my guess now is valves?

see cold start video below.




https://www.youtube.com/watch?v=z05ZShm8Hyk
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r6 99 quill pipe ....

[brythered92]

Also read in a few places that the cold weather could be the main reasons. Some others suggest warming the oil sump and battery gently up with a space heater or similar if kept indoors to assist starting.... I imagine that as cold air is denser could be too lean / oil could be too thick in the cold. Or maybe im just overthinking it all and trying to get out of checking the valves
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r6 99 quill pipe ....

[Nobby the Bastard]

[jaffa90]

Found this about the choke,
https://www.youtube.com/watch?v=Zn50KYvv1rU&feature=youtu.be

Also,
https://www.eng-tips.com/viewthread.cfm?qid=267592

Also nos 5,
https://www.fixya.com/motorcycles/t26853750-bandit_600_96_hard_start_when_hot_but

I suspect 1 or 2 choke / start jets are blocked.