Bike just revvs out on start

[skinnydog0_0]

Hi All,

I have just got the new wiring loom on the bike and started it for the first time since i bought it.
It will only start with some choke (as expected) but as soon as it fires it just revvs out to like 10k

I have cleaned and set the carbs as per manual - the jets are quite bige 124's and it has a K+N filter and full quill exhaust.
I have set all the shims and have a brand new battery.

I managed to get the bike started just now on the choke and as soon as it started revving out i reduced the amount of choke and it died after about 3 seconds.
Now i also hear a knocking/ticking and noticed some white/blue smoke from the exhaust.
I dont want to suspect piston rings just yet as the bike has been stood for quite some time and i was expecting some smoke/moisture from the exhaust.
The cam chain tensioner is about half way through it's travel.
The shims when done were tight, but not rediculous - so i dont think the cam timing is out.

Anyone have any other suggestions as to what it could be?
Also what size compression tester fitting woudl i need for these engines?

Many thanks

[ross46]

Can't remember the exact size, though I think it will need a 10mm adapter, and my bikes done that loads of times before. Normally to do with fuel. Does it when the float bowls are empty. Could also be, throttle cable stuck (have you got the 3mm freeplay?) if you've got the airbox on is it leaking? Have you got the bungs in the airbox in? Try starting it and letting it sit for a second and see if it levels out, if not, try the idle adjuster to bring it back down if that doesn't work, kill it and start checking. Simple stuff first, normally just you've left something out or not connected it. Are the vaccuum pipes on? Good luck

[skinnydog0_0]

Yes I suspected an air leak too, but was nervous about the smoke and ticking/knocking. I am going to get the carbs off again tonight and clean the pilot jets again. The manual shows main jet options up to #100 so mine are massive. I can't get the bike warmed up as its either running at max revs or stalling. I think I'll go back to a full standard set up with a #98 main jet and see how it operates. I'll see about getting a 10mm adaptor for a compression test. Cheers.

[ross46]

Oh yeah, ticking knocking, check your valves as you said the cam chain is fine, though you might want to check the tensioner is ok and in the right way and the tensioner blades aren't broken. And try winding the idle adjuster all the way out and see what it does

[banner001]

my fast "tap-tap-tap" was from a dead rocker arm, if you are opening the top of the engine you might wanna check them all for wear, they tend to wear at the "back" near to where they attach to the rod that holds them all, can be difficult/impossible to see without removing the cam caps, but its something to consider.

[skinnydog0_0]

Quick update,
Just got the head offand it looks like the issue is - the top of the rocker arm that meets the cam has been very badly worn. it has a 1mm indent in it. The cam lobe that acts on this rocker arm has some damage to the inside edge as it must be rubbing in the indent. looks like new cams and at least one rocker arm - but with this one so badly worn i suspect that the others may suffer a similar fate in the not to distant future. I am going to check the valves for starightness in a bit, but the piston tops all look fine and the valves seem to look okay (but thats not to say they are)

Has anyone else had this issue with the top of the rocker arm wearing?
I'll get some pics up in a bit.

Cheers

[banner001]

its fairly common unfortunatly
viewtopic.php?f=117&t=14815

unless the cams are seriously damaged you can put off buying some and just replace the rocker arm...thats what ive done.

on my L4 i had the one bad one, they can be caused by oil starvation, but its most likely due to contaminents in the oil from infrequent oil changes creating a small bit of damage to the hard-facing of the rocker arm...and once that hard facing goes you get a lot of damage fairly quickly.

post up pics if you want, but best bet is to try and find decent second hand, or new rocker arm, new oil and filter, do your valve clearances and check the camchain for tension...top end of the engine will be like new

[skinnydog0_0]

its fairly common unfortunatly
viewtopic.php?f=117&t=14815

unless the cams are seriously damaged you can put off buying some and just replace the rocker arm...thats what ive done.

on my L4 i had the one bad one, they can be caused by oil starvation, but its most likely due to contaminents in the oil from infrequent oil changes creating a small bit of damage to the hard-facing of the rocker arm...and once that hard facing goes you get a lot of damage fairly quickly.

post up pics if you want, but best bet is to try and find decent second hand, or new rocker arm, new oil and filter, do your valve clearances and check the camchain for tension...top end of the engine will be like new

Cheers mate,
Yes the cams do have slight discolouration but they dont look badly worn, even the one on the affected rocker arm. Now i know what the issue is i think i will do as you say and just replace the rocker arm.
The guy who i got the bike from replaced the cam chain just before i bought it - i suspect thinking that this was the cause of the noise that i/he was hearing.
If the new rocker arm solves my issues you have saved me a fair few quid banner001

As per the first post i think i know why the bike was also having issues with the revving out (aside from the rocker arm) the pilot jests seemed to be blocked so to git it ticking over it had to have the idle aduster wound right out to get any fuel - then it just went to 8k+
I was a bit pissed with myself beacuse i forgot to remove and clean the pilot jets first time round.
Hopefully i may get the bike ready for a quick spin before the lovely weather dissapears.

[skinnydog0_0]

Okay, have checked the rocker arm faces and another 4 have scores in them and the suface is starting to flake
The exhaust can also has a flat spot just after TDC so thats fecked too.
I have got a complete head with cams and valves off Ebay so will hopefully be able to just swap the head out complete - if not i shoudl be able to make 1 good one from the 2