Is Throttle Rotation Necessary For Cold Starts?

[guzziart]

Hi All,

My '03 V11 Lemans, when cold, requires a twist of the throttle to start.  The bike has always required a slight throttle manipulation for the engine to start & run when cold according to the previous owner.  I figure the bike is fuel injected (15M PF3C)and shouldn't need anything other than run the "choke/enrichener/throttle plates" to high cam and hit the start button.  When I do the high cam and hit the starter button, the engine cranks and wants to start...sometimes it will start momentarily then stall, other times it will crank and not start.  However, it will always start & run with a little twist of the throttle.  In early 2020, I had some time on my hands and did the "decent tune-up".  IMO, since the tune-up, the difference in overall performance was a huge improvement.  However, the twist of the throttle thing when cold still exists and was wondering if this is "normal".  The owners manual says nothing about throttle manipulation during the starting mode.

I have looked/checked for vaccuum leaks but have found none other than the TB vac ports which I capped off.  The tb shafts have very slight wear/side play but they dont appear to be leaking...the bike only has about 10k miles on it.  The TPS seemed to have a smooth transition though the mv range when I set it...no hiccups.  The mechanical  high cam linkage & tb linkage are in good working condtion..no slop.  The crank position sensor was out for a new oring, found no metal debris on the sensor.  Plug wires & caps were replaced because one cap had tip over damage & high resistance. Air filter was replaced.  Engine & air temp sensors seem to be working and display ambient temps until engine heat causes a rise.

Thanks for reading.

Art

 

[docc]

Yep, same here when cold. Once it has come up to operating temperature, it starts with no throttle even if has sat for a few hours.

[Tomchri]

And she is idling perfectly 1100rpm +when warmed up ?        Engaging high cam before ign on isn't adding any fuel, hitting the throttle ign on will, l think.   If that's the only little procedure needed to get her going, l live with that.   I do my best to have her

running without the throttle linkage connected when tuning.   And they all behave differently, even today's bikes.

Sorry no conclusions,  but many here like to hear other lads experiences with our one of a kind bike.

 Cheers Tom.     

[po18guy]

The M-M gives a prime shot when the pump hits, does it not?

[MartyNZ]

Art, my bike needed a twist to start, just as you described. It came alive with a Ba-boom to wake the neighbors. I always felt bad about getting rpm above idle with low oil pressure. Then I loaded Meinolf's BIN file to the ECU. After that it starts and idles without touching the throttle.

[Chuck]

The Centauro, Mighty Scura, Rosie the Rosso, and a friend's Daytona all start the same way for me. Just crank it, crack the throttle to *just* the right place and it starts right up. They'll crank forever if you don't do that, for whatever reason..

[Lucky Phil]

2 hours ago, po18guy said:

The M-M gives a prime shot when the pump hits, does it not?

Yes. Actuating the fast idle lever is the same as cracking the throttle it's basically a hand throttle or variable throttle stop. The engine ecu has a "cranking enrichment map" to add extra fuel for a pre determined amount of engine revolutions at start up. In the case of the V11 it is for 4000 engine revolutions and is at maximum "richness" from the first revolution of the engine tapering down to zero enrichment until 4000 revolutions have been done. This map is adjustable and one I modified on my bike to assist starting which was initially very hard with the 2 valve start enrichment map percentages. It is also active no matter what the engine temp is so even works with a hot engine. This is why when adjusting the CO level you need to start the engine and wait for around 3-4 min before any CO adjustment can be assessed by engine idling. In addition there is also the enrichment determined by the engine and OAT temp sensors which are added to the base map along with the Cranking map. At extremely low temps all this adds up to around 200% extra fuel at the initial hit of the button. This is also why your tank range is reduced quite noticeably with a lot of cold start cycles esp in cold weather. Add to this the TPS adjustment accuracy, wear in the throttle shafts and, how the air bleeds are set and valve clearances etc and it's a wonder they start at all, lol.

They all start differently but in my experience all need a little throttle when cold. There is a big difference also between manual throttle manipulation and using the fast idle lever and using the twist grip. My bike starts very well using the fast idle lever before you hit the button but not as well if you try and manipulate the throttle by hand. The difference is quite distinct.

Ciao      

[guzzler]

G'day 

Mines the same from dead cold she needs a wee bit o throttle before she ba-booms into life...

Same as Doc's fires first touch of the button after that.

Cheers  

[po18guy]

2 hours ago, Lucky Phil said:

Yes. Actuating the fast idle lever is the same as cracking the throttle it's basically a hand throttle or variable throttle stop. The engine ecu has a "cranking enrichment map" to add extra fuel for a pre determined amount of engine revolutions at start up. In the case of the V11 it is for 4000 engine revolutions and is at maximum "richness" from the first revolution of the engine tapering down to zero enrichment until 4000 revolutions have been done. This map is adjustable and one I modified on my bike to assist starting which was initially very hard with the 2 valve start enrichment map percentages. It is also active no matter what the engine temp is so even works with a hot engine. This is why when adjusting the CO level you need to start the engine and wait for around 3-4 min before any CO adjustment can be assessed by engine idling. In addition there is also the enrichment determined by the engine and OAT temp sensors which are added to the base map along with the Cranking map. At extremely low temps all this adds up to around 200% extra fuel at the initial hit of the button. This is also why your tank range is reduced quite noticeably with a lot of cold start cycles esp in cold weather. Add to this the TPS adjustment accuracy, wear in the throttle shafts and, how the air bleeds are set and valve clearances etc and it's a wonder they start at all, lol.

They all start differently but in my experience all need a little throttle when cold. There is a big difference also between manual throttle manipulation and using the fast idle lever and using the twist grip. My bike starts very well using the fast idle lever before you hit the button but not as well if you try and manipulate the throttle by hand. The difference is quite distinct.

Ciao      

Thank you. I ask because there are apparently some FI systems which send a primer shot through the injectors before cranking begins. I have cycled the key/pump on and off and on again and it does seem to fire off more quickly. It's the effect that might have on the pump and relays that makes me leery of the practice.

[docc]

1 minute ago, po18guy said:

Thank you. I ask because there are apparently some FI systems which send a primer shot through the injectors before cranking begins. I have cycled the key/pump on and off and on again and it does seem to fire off more quickly. It's the effect that might have on the pump and relays that makes me leery of the practice.

I have to agree with the concern that unnecessarily repeated inrush current is not friendly to the relays, perhaps the pump as well.

[guzziart]

Geez, thanks for the quick replies!  I guess I'm good to go then, what you're all describing is exactly what is happening.  Terrific, I can cross that off my "things to do" list.  And to the best of my knowledge and the original owner/po, the bike has the factory map and I'm really not enthusiastic about changing it because it runs great imo.

Thanks again,

Art

[Lucky Phil]

1 hour ago, guzzler said:

G'day 

Mines the same from dead cold she needs a wee bit o throttle before she ba-booms into life...

Same as Doc's fires first touch of the button after that.

Cheers  

Try leaving the throttle alone and applying the cold idle lever instead before you hit the button. How much you ask? Depends how it's adjusted as they tend to have a fair amount of "dead band" if adjusted properly. Move the lever while looking at the mechanism on the r/h throttle body until it starts moving the throttle shaft to get an idea of the size of the dead band then give it a little bit more for a cold start and crank it and don't mess with the throttle. When it fires it will probably go straight to 2000rpm or so and you can then slowly back it off to a high idle of 16-1800 rpm for a minute and then off and use the throttle.

I think playing with the throttle at low cranking speeds isn't the optimal scenario for the ecu trying to apply the correct injector timing duration.

Ciao 

[po18guy]

So my plan is to make a port into the intake boot and give it a spritz of starting fluid. Or not. Actually, if you adjust the fast idle cam to minimum acceptable slack, you can get pretty fair opening with the lever. And, swap out that valve spring on the fast idle cam for say, a ball point pen spring. All it needs is just enough to retract the cam. Helps if the cable is well lubed. Fast idle can then be tweaked with the lever, without it "springing" to the off position. 

Oh, and for those running standard plugs, might try a set of  Iridium. I noted quicker starts after swapping them out. The spark being less shrouded, they have an easier time firing a leaner mixture than the wide electrode OEM plugs.

[docc]

Very good points, as always @Lucky Phil.

I probably leave too much "dead band" (what we Yanks might call "free play") in the high idle system. It is a combination of cable adjustment and the high-idle cam position. I have long defaulted to making sure it does not foul the throttle linkage. I'm sure I could set it closer (less "dead band") and get more out of it without opening the throttle.

Yet, either way, they both nudge the TPS and tell the ECU the same thing, yes?

[docc]

Just now, po18guy said:

So my plan is to make a port into the intake boot and give it a spritz of starting fluid. Or not. Actually, if you adjust the fast idle cam to minimum acceptable slack, you can get pretty fair opening with the lever. And, swap out that valve spring on the fast idle cam for say, a ball point pen spring. All it needs is just enough to retract the cam. Helps if the cable is well lubed. Fast idle can then be tweaked with the lever, without it "springing" to the off position. 

Haha, so, this reminds me of the fairly early idea to swap the High Idle Spring for the Seat Latch Spring and both work better.

Mine did!