Thanks neo,

My understanding of fuel octane is the lower the RON the quicker burning (flame front), I know when advancing the timming people use higher octane to control pinging.

But I am not sure the effects of introducing a quicker burning fuel, is this to aid retarded timming?

Could you kindly explain your understanding of going for lower octaine fuel please?

Also where or how do you obtaine 91, in the UK it's 95 standard upto 99.

Thanks

Paul

Hi, it does sound like it's running lean by what you have described, I had the same problem and everyone was shouting crank seals I replaced them anyway as they are cheap and a dead simple job for me even though I didn't totaly think they were gone. My lean problem I tracked down to carb float height. My bike is running a keihin and everywhere I searched says set it to 19mm. Not true for the Sherco but thats another story, Splat shop now has a blog page on this.

I think the delorto is more forgiving with float height but check it anyway. Phone Chris at Splat shop, He will give you the right info and save you a lot of messing around and wild goose chases.

Hi Paul,

My understanding is based more on personal experience than anything else. As I said I spent a LOT of time trying to fix the hunting but but it came back every time. I was using 98 (with a small Pilot jet) and I didn't want to change that because it gave more zap and power.

I had read on numerous occasions that a larger Pilot cures hunting but you can't do that on 98 because it runs far too rich. And having a larger Pilot jet makes it less prone to carb blockages ....which really added to the confusion of tracking down my problem.

Hmmm... I assuming that RON (Research Octane Number) is a international standard?.... But if 95 is all you have access to then I guess you'll just have to work with that. In Aus we go from 91 to 98.

I'd also agree that giving Chris at Splat shop call is a good idea

Hey Steve, What float height did you end up with?.....I used Vitron seals when I did my Crank seals (not so cheap lol!) and removing the gear pinion on the clutch side can be a real bugger lol!!

Best of luck.

Neo

Thanks Steve,

I found the blog (linked) and it makes sense about the float height effecting the mixture, I presume this would help more with the high revving after releasing the throttle (lean) rather than fixing any idle issues? It does mention that the dellorto carbs can flood the engine due to no overflow so I'll need to be careful.

Neo, regarding the pilot jet, thanks I shall keep this in mind.

Will call Chris tomorrow, I'm a keen fan of splatshop :-)

ALSO - If the crank seals were to have gone, would I not pick this up in a compression test rather than having to rip the engine apart to find? Just wondering if it's easy to diagnose?

Regards

Paul

ALSO - If the crank seals were to have gone, would I not pick this up in a compression test rather than having to rip the engine apart to find? Just wondering if it's easy to diagnose?

Not unless the seals are very, very bad.... A leak down test is better but still no guarantees..... And I must admit that I actually spent more time preforming a leak-down test than I did changing the seals lol!!

All the best either way.

Neo

As neo has quite rightly said it takes more time diagnosing a crank seal than it does to change it. Doing mine cost about 25 quid and an hour of my time. But it's worth it's weight in gold as piece of mind that I don't have to scratch my head and wory about them.

I spent hours messing with float heights taking carb on and of about 10 times till I found the sweet setting. Then that same night I came accross Chris's blog online and my floats we exactly as Chris sets them, could have saved hours of messing.

I seem to recall I set them to about 21mm, But I will have to recheck when i have the bike apart this weekend to do some maintance.

I'm running a 125 main, 48 pilot, 3.5 slide and jjh needle 2nd clip. I will try the 45 pilot back in now I have the floats sweet and see how it runs.

It still seems slightly lean on run down but I have noticed most shercos running a Keihin or dellorto sound about the same. Maybee I'm too fussy and should go and fit a Gas Gas engine in it, That would make the perfect bike for me..

Thanks Steve, I do enjoy working on the bike so may just do them :-)

Today I have adjusted mixture but no difference. I did try to ring Chris but no answer yet.

I don't know if it tells us much but on choke the bike runs perfect.

Does anyone know where to measure the Dellorto float heigh and what it should be?

Google brings up a lot of info, like

http://www.motorcyclecarbs.com/Dellorto_Float_Height_and_Jet__W77C2088.cfm

Thanks, I should not have dismissed searching the web for that answer doh!

I will check these now.

Note rhe PHBL and H float height specs in that article are incorrect!!!!!!!!!!

Parallel is a key word in it, though, and should measure about 18.5mm.

Thanks, just found this out as the float arm housing itself is lower than the quoted 24.

I measured 18 with the carb upside down which is a closed reading in that case?

Some other facts to add are:

Pilot 33

Main 120

Atomiser 270k

Choke 60

Float valve 250

Needle 36 on second setting from the bottom.

So do I need to try different jets if my float height seem to be fine?

Also not sure how crank seals could be the problem if running on choke is fine?

Thanks chaps

I would say go with the 36 pilot, and order the Viton seals from Splat shop, unless he suggests other jetting.

Standard recco is 98 RON for uk fuel as I recall.

Pull the mix screw and use carby spray to insure passeges are flowing well to the two tiny holes in the bore of the carb. Tank clean, fuel cans clean, and I mean NO water or dropout condensation.

Just a couple more ideas, Check for leaks around base gasket with some wd40 while running, make sure engine is cool so just after starting. look for bubbles of a change in the engine note.

Strip and clean the fuel pump just for good measure.

They normally run down sooner with the choke as they are over rich with the choke on.

Im starting to think this is a sherco thing with mine, The bike does ride superb, I just have ocd when it comes to carburation!!!

Thanks chaps,

I think I will order a larger pilot, to see if I can cure idle but as Steve says it's easy to become obsessed with getting it just right :-)

The annoying over revving is the goal and I have even had the shop say it's more than likely crank seals, especially the flywheel side.

So I'm now the proud owner of a flywheel puller and two crank seals, oh and a new gear leaver as I was in the shop with all these shiny objects in front of me...

I'm planning to ride Wednesday then will fit the seals, I'll post back any results.

Cheers

Paul

Just spending some time reading through the forum, and discovered a thread on mixture ratios.

The shop I bought the bike from told me to run a 50:1 mix so I mix up 100ml to 5l where others are running a 70:1

Could my bike have been setup for a different mixture by the previous owner?

What are the effects of too much oil in the fuel could this add to my lean run on issues?

Thanks yet again.