Help needed - Mirage TS '82 not running correctly

[Paul LeClair]

You forgot cracked manifolds, Paul.  Brake cleaner sprayed on the manifolds at idle will show if there are any leaks in that area.

Maybe the poor thing is just tired...

piet

Hi Piet

I have accumulated a modest collection of broken intake manifolds, usually they are pretty obvious when the manifold is unbolted and it falls apart.... but good point.  Now most of the bases have been covered, will be interesting to see what Martin's report back turns out to be.

By the way, wouldn't 260 main jets in Dellortto carbs be for exotic alternate racing fuels that need to be introduced into the engine in massive quantity?

Paul LeClair

 

[sfcpiet]

By the way, wouldn't 260 main jets in Dellortto carbs be for exotic alternate racing fuels that need to be introduced into the engine in massive quantity?

Perhaps if it's running on dope, but then I'd suspect 260 will still be a bit small...  Big brit singles on alchohol-based fuels needed mains in the region of 1000!  Think I found 900 specified for a BSA Gold Star on dope in an old Amal catalogue.  Not sure if it is directly comparable to Dellorto jet sizes, but a big whopping hole nevertheless!  Probably close to what speedway bikes need as well.

Relatively "normal" petrol-based fuel won't require such large jets.  Methanol and similar stuff are quite low efficiency when compared to petrol, hence the need for it in bucketloads!  Main advantage is the compression can be pushed through the ceiling to gain power.

piet

 

[CLEMTOG]

hello Martin, yu have obviously got work to do on your TS, but here is a quick check which has not been mentioned, lift the hinged seat and look under the right side top frame rail, here you will see a tag welded on which is the earthing point for both the two sperate sides to the ignition system, there are two very (very very) short wires exiting the main wireing loom and crimped onto a common ring terminal for both wires, two things happen a lot, one  of the wires partially seperatesfrom the ring end, giving you a voltage, but not a good connection, the other is where those wires cross the tin ware, there is a strong possibility of them rubbing through the outer insulation and making a poor earth contact with the tin rather than at the ring, it might be sound, but maybe not, I have seen quite a few bikes with this damage and it happened to my own TS but took me weeks to find, because the bike did run, although not very well.The repair that I instigated was to solder longer tails from the loom (so they are notunder stress) and also use two rings instead of one.
CLEM

 

[Kilmer]

Hey all,

First of all I want to send a "thank you" to all that took the time to reply on my post - It has been greatly appreciated.
I took all of the advice into consideration and decided that a more thorough investigation was needed. And boy I was glad that I did.

The following was found.
? Found a defective accelerator valve in one of the carbs.
? Gaskets in general were worn on all 3 carbs.
? Choke pistons was worn on all 3 carbs (rubber innards)
? O-rings on intake manifolds was worn out ? all 6 of them!
? The original pickup bush on the crank was loose!
? Rubbers form carbs to air box was mounted the wrong way, making room for air intake on carbside of rubber.
? Camchain was worn

The following was mended/done.
? I took the carbs apart and cleaned every bit of them. Bought new of almost everything including gasket kits, choke pistons, accelerator valve, needle, jets and all.
? Bought new O-rings for the intake manifolds
? Bought new shims and readjusted all the valve cleareances.
? Bought new camchain and fitted it.
? Bought a Moto Witt DMC2 ignition.
? Did a new compression test ? this time with throttle @ wide open and got results at around 120 PSI on all 3 cylinders (I believe its somewhere in the middle = semi worn barrels)
? Stripped the air box innards

It now runs with following specs.
? 256AB needle jet
? K1 needle
? 65 pilot jets
? 135 main jets
? DMC2 ignition with a 36 degree advance curve (setting 6).

Did my first test run on it last night and what a difference! There?s no more ?holes? in the acceleration ? it runs clean and pulls even on acceleration. I did have problems getting it to idle correctly but assumes that I need to adjust the carbs a bit more.
The plugs seems on the lean side though ? did only 15 km. so need to go for a longer ride to be certain.

I'll post an update as soon as I get the little things sorted

Best regarts,
Martin

 

[Dellortoman]

Well done that man.

Just a couple of fine tuning suggestions:

It's very difficult to read spark plugs with unleaded fuel. If you're expecting colours like we used to get on leaded fuel, then you could interpret the unleaded colour as alarmingly lean.

With the jets you specified (135 main jet is on the large side) it's probably running rich at WOT. Find a bit of quiet road where you can ride it at full throttle long enough to do some tests. Back the throttle off a bit from wide open. If the bike surges briefly before slowing down then it's too rich.

Best bet is to book a session on a dynamometer, which takes all the guesswork out of tuning. Take a handful of jets with you. Check some alternative advance maps while you're at it. You might find it performs better with a bit less advance.

 

[Kilmer]

I've just come home from an hour of testing - did a couple of maptests on the ignition and found at 32 degree max advance to work better 

did some full throttle testing as well, which is a no go - as soon as i turn the throttle wide open, the engine starts to cut out. not completely but enough to make me nerveous and release the throttle again.

no doubt that the intial result is FAR better than before i started messing around - its just not perfect yet. >

got a couple of ideas as to next step.

• try a 145 main jet
• check stator plate and see if timing got screwed somehow
  

any other suggestions?

/Martin

 

[KERMIT1200]

Hi Martin,
To much fuel (to big main jet) can stop the engine from reving.The pilot jet quoted is on the large side.I'd be interested to know what the mixture skrews are set to?
Run the bike up on a dyno will/should allow you to set carbs up correctly.

Andy

 

[Dellortoman]

My bet is that it's bogging down at full throttle because it's too rich, so a 145 won't fix it. You need to go down in main jet size. Try 125 or 120.

 

[AndyW]

From memory my '78 Mirage has 55s and 145s installed and runs fine from 2k to whatever and at all throttle openings. I think these are the jet sizes recommended in Parker's book. Are Slater and TS Mirage engines configured the same; 4C cams and 8:1 compression?

 

[CLEMTOG]

no Andy they are not
as standard the first series one TS's had the disastrous Jota big valve head but A11 cams and Red's favourite tractor pistons,
later series ones lost the big valve head and the stupid short valve springs as did the series two's, they all had A11 cams as factory but many were fitted (even from new) with 4C cams, this could have been for a press bike, or the more sporting requirments of the fresh owner,lots were retrofitted with higher comp pistons, I did come across one with 7C cams in it, which at first seemed to be the cause of a lumpy idle and poor starting, but this was disproved by fitting some 4C's and it persisted,in those days 4C'as were two a pennym now they are not, I still have the 7C cams.
CLEM

 

[mauricejota7604]

I wonder if the filters in the petrol taps are blocked and not allowing enough fuel flow at high revs remove your tank empty the fuel turn it upside down and unscrew the taps I bet the plastic filters are blocked to the shithouse

 

[tom3c75]

Would agree that 135 mains are too big, esp if the pistons are low comp. 
For a 1200, 65 pilots may pass, however.
My 82 1200 runs very well on 125 mains and 60 pilots. 
This airbox internals have been gutted and has aircon gauze for the air filter.
Bike has std pistons and A11's.

 

[Kilmer]

Just an update on all of your fantastic suggestions - I really appreciate all the feedback that has been given! What a great forum  8)

I?ve just ordered new mains and idle jets ? two sets of mains 125?s and 130?s plus a set of 60 idle.
As the needle was changed from the stock K14 to K1 and the airbox innards ripped, there?s no need to compare my specs to those listed with the ?stock? Mirage I guess.

Bought myself a strobe ?gun? and did an ignition test yesterday ? why on earth I didn?t have the sense to do this earlier beats me ? but it turned out that the ignition was slightly off. The advance was short (not 32 degrees at 4.000 rpm?s).

I?m going to book a session on a dynamometer sometime next week ? need to keep it from the girlfriend as way to many expenses is piling up and she?s begun to notice 

Also I did a check on the fuel taps ? nothing wrong there.

/Martin

 

[Kilmer]

Ok - so I'm unsure if it the best idea to awake my original post (being from 2014), but here goes.

Due to more kids and family stuff the project has tanke way longer than anticipated. The bike has been paintet in the original colours now, the engine fairing bracket has been made and only the decals are on the to-do list (on the cosmetic to-do list, that is).

Regarding my carbs problems i've given up - took it to and old Laverda mechanic here in DK who had it for a couple of weeks - best result yet, but utter worthless in the end. About 5.000 rpm the engine stalls.. Only at 100% throttleopening does it reawake which makes for extremely odd driving in daily traffic 

Soo.. the mechanics input is that the carbs are done (worn beyond repair) and new ones needed. The snag is that Dellorto does not produce the 32mm carbs which goes on the aluinlets anymore.. They've switched to rubber inlets, which here in DK sets me back further on $$.

My question for anyone kind enough to read this post.
1. Should I try to source any used original 32mm dellortos? If so, anyone having at complete set in good working order laying around?
2. Go with somekind of alternative? Mikuni's or other? If so, any "plug and play" solutions out there? 
3. Some great answer I havent thought of at question to..

Attatched a picture of the current state of my TS 1200 - by now far more expensive than what its worth 

Best regards,
Martin

 

[CLEMTOG]

hello Martin, if your carbs do really need changing you could try this (picture below)

what it is made up of, is RGS carbs (my ones obtained from a crashed bike with 14,000 kilometres and then left for 20 years un-repaired)
and a set of Jota 120 inlet rubbers (make sure you get genuine items not Moto Guzzi ones as they are too long)
and a set of alloy inlet stubs from a seller on E-bay , he is called Ellegog,

This gives you the access to use the later RGS carbs which in 32mm size cannot be obtained as new items, but Dellorto do have them in 36mm size and Ellegog does a tapered inlet stub to suit these, all the new bits you bought for the PHF carbs will interchange with the RGS carbs

and my bike is also a TS, none other than the worlds most famous one, known everywhere as "The Old Girl" you can ask Jens Kronberg, or Preben Ingermason or Kurt (another TS) My memory is getting bad and I know at least another 4 Danish Laverda guys, but its gone, for now at least.
CLEM