Poor/No idle from cold 851 SP2

leylandracer

Just a quick question relating to my SP2.....

From cold the idle is really poor, more like it wont idle, when warm all is fine, someone mentioned this is fairly norm on a SP2?? :-( Any suggestions.....
Thanks
Steve

rxs51

Can not suggest a cure but my early (1989) 851 is the same so would be interested to know whether they really all are like that.

AJV

Don't worry It's normal, my SP 2 & 3 have been the same since purchase back in 94, later 888's had a fast idle switch to keep the engine running from cold starts. Desmo engines arn't like modern engines they should be fully warmed before being ridden.

Simply tickle the throttle and enjoy the sound for a few minutes before each ride...

Jafa

My SP3 won't idle either when cold either, I have to hold the throttle for about 10 minutes before it'll idle by itself.

When I had it stripped down I removed the throttle bodies as a unit from the engine. Since I've put it back together I haven't checked the TPS or synchronisation of the throttle bodies. Over on Ducati.MS resetting the TPS seems to fix a lot of "poor / no idle" complaints. I will try it one of these days......

Brad has an excellent write up and instructions on how to reset the TPS here:

http://www.bikeboy.org/ducati4vthrottleb.html

All you need is a multimeter set on mV.

Another good article to read while trying to get your head around it:

http://alexfischer.de/documents/techn_Dokumente/Einspritzung_Tips_engl.pdf

griff851

At 40-45°C water temp mine goes all by itself. Bevels are the same. Handy, as mentioned for warm up. However, it aludes me just now, somebody mentioned mapping something.

While your standing there
waiting for self sustain to happen might as well hold the clutch in. I belive it can be worth up to 10,0.00 km of aluminium clutch life. I use a tie wrap. The low pulse rate at idle makes the drive tabs into little hammers.

900SL

Ticks over beautiful.! ...
does a sneeze and stalls...
It's a character I'd say...😉

Mr.R

Brad will know the answer to this (my) question:-
Are the SP2's fitted with the lighter weight closing rocker return springs?
If they are this could be the reason for the poor idle...

My standard '92 851 ideled perfectly at between 800-1,000 rpm, no matter how hot or cold the weather from start up.
This was nothing to do with me as it did it from when I bought it with just under 6,000 miles on the clock until around 20,000 miles, which was when I tuned it/opened it out to 916cc's.

I've found quite a few 851/888/926/916SP's where the owners have complained about poor idling? When I've checked the bikes I've found the idle set at around 1,000 rpm, so I reset them to idle at 1,500 rpm and in almost every case the poor idle "problem" has gone away.

My tuned 851/916cc fitted with 9*6SPS T1 cams and lighter flywheel etc idles a 1,500 rpm, when it's warm but until then it needs a few more revs. To this end I fitted a 916 throttle with it's "Fast Idle" button.

Steve R

Jasper

My SP5 is the same. It has a fast idle throttle from a 916, it warms up and then will stutter, sneeze and then stall. Its all character!

brad black

sp2 should have the later (heavy) closing springs i think. but that could be crap.

i did an eprom for a local one with a spark map rpm break point at 1,200 rpm, which allowed me to add a heap of advance at 1,000 rpm at idle. so when it was cold it had 30 degrees of advance, and at 1,200 rpm it was back to 15 degrees to hold the idle speed. you can turn on the key and hit the button without touching the throttle and it will fire and idle until hot without issue.

std they have 10 degrees advance at idle. more advance helps with the long cam duration. not idling cold is std.

got2Lev8

FWIW My 90 851 DS originally purchased in the UK had the light race springs and 29/33 valves. The heads are matching and stamped 90 2nd month. It also had 94mm jugs. However, those are stamped 1 (91) so probably an add-on.

I initially used the heavy springs with my 748 heads. And the bike fired right up the first time after rebuild. But then after having to sort out an oil leak in my vert head, I went back to the lighter springs because I had read that it's better for rocker wear. I did end up adding a fast idle from 916 and I do have to use it to warm up...usually ticking at a hair over 2,000 until the temp hits 50.

I do plan to re-sync the throttle bodies as well as resetting the tps voltage over the winter as starting and restarting is not always straightforward.

Robert

brad black

if the closing clearances are good (tight) the soft springs aren't that big an issue. probably not a good combo with the 1.5mm collets tho when you want to avoid regular adjustments.

Mr.R

With what Brad's just said, I quite fancy using a set of the lighter springs in my 955cc motor.
I already run tight (2mm or under) closing clearances along with MBP collets.
Any ideas as to where I can still get the lighter springs?

Steve R

MarkT

brad black wrotesp2 should have the later (heavy) closing springs i think. but that could be crap. i did an eprom for a local one with a spark map rpm break point at 1,200 rpm, which allowed me to add a heap of advance at 1,000 rpm at idle. so when it was cold it had 30 degrees of advance, and at 1,200 rpm it was back to 15 degrees to hold the idle speed. you can turn on the key and hit the button without touching the throttle and it will fire and idle until hot without issue. std they have 10 degrees advance at idle. more advance helps with the long cam duration. not idling cold is std.

Brad/Steve-

My '89, '90, my SP2, and all my Corse's have had the very light springs.

guillaume69

Reviving this old thread as I am glad to have found this info. ( @mike the search fonction works a treat!)

I was surprised that there is no fast idle device on my new to me SP2. Even more so after looking at the 1990 851 Strada user manual, that shows one and depicts it’s use during cold start. Now I understand it’s not the case on SP2s and that it’s all about their « character »! :-)

For the record, my SP2 starts like a charm but requires the throttle to be held for 3-4 minutes until it holds a small 1000 rpm idle. Once it gets near operating temperature (60-70 celsius), it then idles perfectly at 1100 rpm.

KevB

guillaume69 Yep it's a pain! I use a throttle clamp for 5-10 minutes while I am putting stuff on to get ready. Don't risk riding until it will tick over. They are a right old lump to support if they cut out when turning into traffic… Ask me how I know…!

patrick

Install first a 916 throotle handle with the iddle button. A way to improve is to change the injection ramp by one with the airbleed screws (888, 916, S4R etc…) but SP2 is a double injectors? Also a modified fuel map can help.

guillaume69

Thanks much for your advice Patrick.

But as far as I am concerned, their is no modifying this bike’s injection or throttle set-up in any near future. Or any future at all. ;-)

guillaume69

Throttle clamp?

Would have a picture, by any chance ?

KevB

guillaume69 Pretty much like this:

https://www.amazon.co.uk/Motorcycle-Throttle-Handlebar-Motorbike-Scooters/dp/B0895VTQ6Q