Cold starting issue

Need advice on which oil to use or which tyre best suits you? Share your topic and get help here.
Post Reply
jchesshyre
Posts: 590
Joined: Wed Jun 15, 2016 9:09 am
Location: Chester, Cheshire

Cold starting issue

Post by jchesshyre »

Since I swapped my carbs for another set, my bike is difficult to start from cold. It otherwise runs great with these carbs, better than the previous ones (think they have less worn needle jets, though the reason for swapping was a seized pilot mixture screw). Once warm it starts literally on the button, like it always has.

It is hard to start whatever the choke position, though the most successful method seems to be crank it with no choke and certainly no throttle, then when it eventually fires (usually after a loud backfire), gradually pull the choke out to give a high idle then reduce this after 20–30 seconds.

I never used to need to do this before changing the carbs out – my normal cold start procedure was pull the choke out roughly half or three-quarters and it would fire up after a couple of revolutions.

I have replaced the battery for good measure but this hasn't helped. I've also cleaned up the starter positive terminal which needed doing, but this too has made no difference.

I've tried various idle mixture settings – no change. Carb synch – no change.

Given that the bike runs brilliantly, and this change has only come after swapping the carbs, this suggests to me that it's the carbs I should be looking at and probably the enrichener circuit and needle/cable operation. I should say though that once the engine has started, the choke has the expected effect of raising the idle speed to c. 2000 rpm and appears to operate normally.

But does anyone have any pointers or has experienced a similar thing?
MK_WF
Posts: 130
Joined: Mon Aug 31, 2015 6:02 pm
Location: Wolfenbuettel/Germany
Contact:

Re: Cold starting issue

Post by MK_WF »

That sounds like what mine has developed since half a year or so.
Checked everything like air filter and installed new plugs, but the behavior is still there.

Once it even refused starting at all, but that was due to a weak battery dropping below 7V when cranking. I've installed a new battery, but couldn't test due to 30cm of this icy whitish powder outside.

The last diagnosis with a Lambda probe was that it's running pretty lean directly after starting with choke.
Cranking with going to WOT and then releasing is the most successful method, which tells me that more fuel will help.
My suspect is a clogged choke-jet, that flows less fuel than required.
Unmounting and ultrasonic cleaning would likely heal that, but as long as it's still starting somehow, I'm too f...in lazy 😁

On my RD350's a bad starting behavior is a sure indicator for bad compression. Had to revise both of mine just recently for having stuck rings / carbon buildup.
Unfortunately my pressure tester didn't fit the VTR, but I now have a new one and can do it when spring comes.
Bye
Martin
jchesshyre
Posts: 590
Joined: Wed Jun 15, 2016 9:09 am
Location: Chester, Cheshire

Re: Cold starting issue

Post by jchesshyre »

Yeah low compression has crossed my mind (the bike has 106,000 miles on it after all), and I too have a gauge but without the right size adapter for the VTR. HOWEVER, it didn't do this at all before swapping to different carbs, 1000 miles ago at the beginning of November. Also power is definitely not down, it feels fantastic and often tries to wheelie in 2nd gear.

The only other changes I've made, at the same time as swapping the carbs, is changing the air-cut valve hoses on these carbs to silicone hose (though if these were leaking I'd get popping on the overrun), and also changing the fuel tap vacuum hose to a silicone one. But I assume if either of these were causing problems it wouldn't be limited to cold starts?

When I have a mo maybe tomorrow I'll have a look at the choke needle operation and blow the choke circuit passages out with carb cleaner to see if this makes any difference.
jchesshyre
Posts: 590
Joined: Wed Jun 15, 2016 9:09 am
Location: Chester, Cheshire

Re: Cold starting issue

Post by jchesshyre »

I'm pleased to say this was just down to the fact that Halford's had sold me a dodgy battery. I should've taken it straight back when found that it was discharged when got it home after buying it back in January (and also because it was labelled Activation Date July 2019!).

Took it back today, they tested it and the machine said 'REPLACE', so they gave me a replacement. I fitted it earlier, pulled the choke lever halfway out, and the bike fired up immediately, on the button, like it used to.

I'd put it down to the carbs because I'd swapped them at the same time as replacing the battery back in January, and assumed the battery would be good. Should've trusted my own carb setup abilities over Halfrauds' battery maintenance abilities.

Happy days.
felix barrao
Posts: 100
Joined: Sat Sep 08, 2018 4:20 pm
Location: Zaragoza ( Spain)

Re: Cold starting issue

Post by felix barrao »

Sometimes if the voltage drops a lot in the crancking, the cdi has not enough voltage to work properly.

Nice to know that is working again.
MK_WF
Posts: 130
Joined: Mon Aug 31, 2015 6:02 pm
Location: Wolfenbuettel/Germany
Contact:

Re: Cold starting issue

Post by MK_WF »

That was exactly why I replaced my battery.
Glad to hear a new one has cured the effect. (couldn't test mine due to winter weather, yet)

I noticed that longer cranking was required and though it didn't sound like the battery would have a hard time, I measured battery voltage during cranking.
Our German VTR "pope" Higgens (vtr1000.de) says it shouldn't drop below 10 V - mine partly was at 7.x V.
And as I have an Ignitech box to create the spark, they list a minimum operating voltage of 8V in their specs.

The old one was in the bike when I bought it 5 years ago, so I guess it has had it's life.
Now I'm using an Intact AGM battery (because they support German Moto 2 rider Marcel Schrötter)
Bye
Martin
User avatar
sirch345
Site Admin
Posts: 21669
Joined: Mon Aug 25, 2003 10:35 pm
Location: The West Country.

Re: Cold starting issue

Post by sirch345 »

jchesshyre wrote: Mon Feb 15, 2021 9:10 pm I'm pleased to say this was just down to the fact that Halford's had sold me a dodgy battery. I should've taken it straight back when found that it was discharged when got it home after buying it back in January (and also because it was labelled Activation Date July 2019!).

Took it back today, they tested it and the machine said 'REPLACE', so they gave me a replacement. I fitted it earlier, pulled the choke lever halfway out, and the bike fired up immediately, on the button, like it used to.

I'd put it down to the carbs because I'd swapped them at the same time as replacing the battery back in January, and assumed the battery would be good. Should've trusted my own carb setup abilities over Halfrauds' battery maintenance abilities.

Happy days.
As Martin said, I'm also glad too hear you've fixed the problem, well done :thumbup:

Chris.
User avatar
8541Hawk
Posts: 2066
Joined: Sat Jul 21, 2012 5:21 am
Location: Bella Vista, AR

Re: Cold starting issue

Post by 8541Hawk »

jchesshyre wrote: Sun Feb 14, 2021 8:38 pm The only other changes I've made, at the same time as swapping the carbs, is changing the air-cut valve hoses on these carbs to silicone hose (though if these were leaking I'd get popping on the overrun), and also changing the fuel tap vacuum hose to a silicone one.
Just an FYI in case of future issues....gasoline and silicone do not play well together.
The gas will cause the silicone hoses to break down :thumbup:
Loud pipes don't save lives, knowing how to ride your bike will save your life.
jchesshyre
Posts: 590
Joined: Wed Jun 15, 2016 9:09 am
Location: Chester, Cheshire

Re: Cold starting issue

Post by jchesshyre »

8541Hawk wrote: Wed Feb 17, 2021 8:48 pm Just an FYI in case of future issues....gasoline and silicone do not play well together.
The gas will cause the silicone hoses to break down :thumbup:
Thank you for the heads-up! Do you suppose this will be OK for the air-cut and fuel tap vacuum hoses though? I don't expect the air-cut ones will touch any petrol, and the fuel tap vacuum one only a residue (if all's working normally).
tony.mon
Posts: 15943
Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: Cold starting issue

Post by tony.mon »

Ethanol in the fuel will probably make it worse...
It's not falling off, it's an upgrade opportunity.
User avatar
8541Hawk
Posts: 2066
Joined: Sat Jul 21, 2012 5:21 am
Location: Bella Vista, AR

Re: Cold starting issue

Post by 8541Hawk »

IMHO it's kind of like the CCT situation. They might work just fine with no issues or it might fail tomorrow.

The ethanol will actually make the silicone happy.....lol
The vacuum tap would probably be the first to go, in that the petrol vapors will soften it which can cause the line to collapse.

The air cut offs probably not a big issue but something to keep in mind if a weird issue pops up later.

Alcohol powered stuff run silicone fuel lines as alcohol dissolves rubber....why the ethanol in the petrol can cause issues.
Petrol powered stuff run rubber fuel lines as petrol dissolves silicone.....

:thumbup:
Loud pipes don't save lives, knowing how to ride your bike will save your life.
tony.mon
Posts: 15943
Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: Cold starting issue

Post by tony.mon »

I can live with stuff failing tomorrow.
Just not today.

It's alcohol in antifreeze, isn't it?
I wonder why they use rubber coolant hoses as standard...
It's not falling off, it's an upgrade opportunity.
jchesshyre
Posts: 590
Joined: Wed Jun 15, 2016 9:09 am
Location: Chester, Cheshire

Re: Cold starting issue

Post by jchesshyre »

Thanks for the warning...I've ordered a length of this which hopefully will fit the bill https://www.veewee.co.uk/186vg0010

Antifreeze – glycols aren't alcohols per se, they are diols, but maybe antifreeze does contain alcohols too, I'm not sure...either way 'rubber' (whatever type the OEM hoses actually are) is clearly OK with it.
jchesshyre
Posts: 590
Joined: Wed Jun 15, 2016 9:09 am
Location: Chester, Cheshire

Re: Cold starting issue

Post by jchesshyre »

Damn didn't notice in the photo that that hose is braided! Don't like how that adds bulk and reduces flexibility.

Anyone know of a source of good 3.5 mm plain rubber vacuum hose? I struggled which is why I opted for silicone eventually.
MK_WF
Posts: 130
Joined: Mon Aug 31, 2015 6:02 pm
Location: Wolfenbuettel/Germany
Contact:

Re: Cold starting issue

Post by MK_WF »

After the first 3 spring rides, I dare say the new battery helped in my case.
Bike started quite normally, even after having stood for a few weeks.

As a security measure, I have ordered a voltmeter from Alibaba to monitor the battery and charging system.
The quality was astonishingly good and the display is bright enough to be read in sunlight.
https://a.aliexpress.com/_mrKg24r
Bye
Martin
Post Reply