Dellortoman
Hero member
- Location
- Tasmania, Australia
That's useful info Piet. The rubber mounts on my bike seem very solid, so they must be in good nick!
R
Reggie3cl
Guest
Rubbers are new and mounted on spigots. Carbs are supposrted at both ends (am using the airbox and standard rubbers) Carbs seem to shake around much more than the engine and only really go mental at certain revs- maybe 3 or 4000? The rubbers between the carbs and engine are quite soft, it must be said.
Cam, what did you tie the carbs to? I've got the tank off at the moment so could experiment a bit today. I've even got a bit of actual fencing wire to use- well, I am married to a New Zealander...
Cam, what did you tie the carbs to? I've got the tank off at the moment so could experiment a bit today. I've even got a bit of actual fencing wire to use- well, I am married to a New Zealander...
Reggie,
The engine shouldn't be able to move around much. If your rubber mounts are soft, they may well be the culprits. Check for rubber seperating/ed from the inners or outers, this can give the engine more space to wobble around in. Fuel frothing and starvation at certain revs would be the result.
piet
The engine shouldn't be able to move around much. If your rubber mounts are soft, they may well be the culprits. Check for rubber seperating/ed from the inners or outers, this can give the engine more space to wobble around in. Fuel frothing and starvation at certain revs would be the result.
piet
R
Reggie3cl
Guest
Dunno what the mounts are like- and if they are buggered are replacements available? In the vid the engine seems fairly smooth and certainly riding the bike I don't have a problem with vibes.
As Cam said, it seems the carbs reach a point where they vibe, and then as revs rise they stop. Who knows what is happening as I go along, but clearly the way the plungers are being destroyed vibrations are getting through.
I've mounted a sort of damper for the choke rod made out of very dense closed cell foam just to see if that helps the choke rod, but I think ideally I'd want something similar but wider made in nylon to support the rod as it is free to rattle around A LOT. It'll still be able to rattle side to side to a certain degree, but at least not up and down which seems to be what is causing the damage. Can't see me drilling the bodies to fit the ball bearings somehow. :
Haven't got a mill to make what I want- anyone care to help? - can supply drawings...
As Cam said, it seems the carbs reach a point where they vibe, and then as revs rise they stop. Who knows what is happening as I go along, but clearly the way the plungers are being destroyed vibrations are getting through.
I've mounted a sort of damper for the choke rod made out of very dense closed cell foam just to see if that helps the choke rod, but I think ideally I'd want something similar but wider made in nylon to support the rod as it is free to rattle around A LOT. It'll still be able to rattle side to side to a certain degree, but at least not up and down which seems to be what is causing the damage. Can't see me drilling the bodies to fit the ball bearings somehow. :
Haven't got a mill to make what I want- anyone care to help? - can supply drawings...
Reggie,
The bores/cavities for the springs and balls should be present. Maybe fitting only one of the springs and balls is sufficient to stop the choke bar from rattling around. Is there no pressure on the return spring when the choke is not deployed? Give that spring a bit more pressure as well?
My RGS has a slightly "rough" spot at around 2500-2800rpm. Quite smooth below, very smooth above...
piet
The bores/cavities for the springs and balls should be present. Maybe fitting only one of the springs and balls is sufficient to stop the choke bar from rattling around. Is there no pressure on the return spring when the choke is not deployed? Give that spring a bit more pressure as well?
My RGS has a slightly "rough" spot at around 2500-2800rpm. Quite smooth below, very smooth above...
piet
R
Reggie3cl
Guest
OK, checked for the holes for the springs- seems like there is one in the centre carb- was able to locate a bit of bent wire in the hole, although not see it. There has never been a spring in there as far as I know as I have not had cause to take the rod out in the 7500km they have been on the bike.
The indents for the ball bearings on the choke rod would not work in the positions needed- they are in the correct position for the screws holding the plunger tangs in place. I suppose one ball in the centre carb would help, but of course the rod could still rattle around as it is not properly supported at each end. The springs on the choke rod are reasonably strong (so to speak) - could add a couple of washers in between the two halves to beef them up.
Photos showing where the ball and spring cavities aren't, as well as the foam damping bodge which would last five minutes but which might give an indication wether a nylon support would work- easier for me than drilling the carbs. Note the choke is 'on' in the photos.
RH carb (no hole) You can see clearly how large the hole in the boss in the carb is compared to the rod. Why is that?
Foam bodge :
Wire hooked into spring hole
LH carb (no hole)
PS Just run the bike up- I think the foam support is helping, although it obviously won't last. The rod has been cut on the RHS which may indicate the it is the wrong way round. This may be deliberate, I don't know, but it may mean that switching it round will put the indent for the ball to locate in in the correct position.
I think the ball being in position and a nylon support between the left and centre carbs would minimise the shaft's vibration.
Vibration is worst between 2500 and 3000rpm.
Rotten old bikes, I bet I'd love a KTM Super Duke GT....
The indents for the ball bearings on the choke rod would not work in the positions needed- they are in the correct position for the screws holding the plunger tangs in place. I suppose one ball in the centre carb would help, but of course the rod could still rattle around as it is not properly supported at each end. The springs on the choke rod are reasonably strong (so to speak) - could add a couple of washers in between the two halves to beef them up.
Photos showing where the ball and spring cavities aren't, as well as the foam damping bodge which would last five minutes but which might give an indication wether a nylon support would work- easier for me than drilling the carbs. Note the choke is 'on' in the photos.
RH carb (no hole) You can see clearly how large the hole in the boss in the carb is compared to the rod. Why is that?
Foam bodge :
Wire hooked into spring hole
LH carb (no hole)
PS Just run the bike up- I think the foam support is helping, although it obviously won't last. The rod has been cut on the RHS which may indicate the it is the wrong way round. This may be deliberate, I don't know, but it may mean that switching it round will put the indent for the ball to locate in in the correct position.
I think the ball being in position and a nylon support between the left and centre carbs would minimise the shaft's vibration.
Vibration is worst between 2500 and 3000rpm.
Rotten old bikes, I bet I'd love a KTM Super Duke GT....
Gravelroad
Hero member
- Location
- Central Europe
Looks like the hole in the RH carb has already been clapped out by the vibrating rod, probably easy to cure by inserting a bushing. Rubber spigot of RH carb is cracked. Didn't you mention they have been renewed recently?
R
Reggie3cl
Guest
Is it? Blimey, better check that.
Pretty sure they are new when the carbs were changed from Dellortos. Could be surface deterioration...I'd be very unhappy if the (new!) carbs had been wrecked so soon- seem to remember that the rod seemed loose when I was fiddling around sorting the choke cable.
Dellortoman
Hero member
- Location
- Tasmania, Australia
It's strange that the left and right carbs have no hole for the choke detent mechanism while the middle carb does. It's normally the other way around. If you re-read Red's post, you'll understand that it should be the opposite. Seems you may have a cobbled together set of carbs.
If your outer carbs don't have the drilling for the choke detent, then they may not have needle roller bearings for the throttle shaft. It also makes me wonder which carb (if any) has the accelerator pump. There may be more issues with your set of Mikunis than just the choke assembly.
Seems your carbs need to be set up properly. I could do that for you, including installing throttle shaft needle rollers if necessary, but it would involve postage to the other side of the world and back. I reckon your best bet would be to take them to Keith so he can sort any issues.
If your outer carbs don't have the drilling for the choke detent, then they may not have needle roller bearings for the throttle shaft. It also makes me wonder which carb (if any) has the accelerator pump. There may be more issues with your set of Mikunis than just the choke assembly.
Seems your carbs need to be set up properly. I could do that for you, including installing throttle shaft needle rollers if necessary, but it would involve postage to the other side of the world and back. I reckon your best bet would be to take them to Keith so he can sort any issues.
R
Reggie3cl
Guest
Aye, well we'll be coming to the end of the season in a couple o' months so I can take them off then. The centre carb has the accelerator pump and I think the outer two have needle rollers, but I'll have to take a closer look. Doubt there was much cobbling going on, Keith put 'em on the bike.
If I can find someone with a mill and a 25mm square block of nylon I can have a support for the shaft made and that together with replacing the ball in the centre carb should prevent any further problems, or at least slow them right down.
Everything eles is good- the 20 pilots at 1/2 a turn are a big improvement- might even be able to go a bit leaner and response everywhere is excellent.
If I can find someone with a mill and a 25mm square block of nylon I can have a support for the shaft made and that together with replacing the ball in the centre carb should prevent any further problems, or at least slow them right down.
Everything eles is good- the 20 pilots at 1/2 a turn are a big improvement- might even be able to go a bit leaner and response everywhere is excellent.
Dont seem to have as much vibe's on my carbs as you... though there is a bit but when I was riding yesterday did the old hand on the carb trick and didnt seem that bad and was consistant with the vibes on the tank and the other odds and bods.
Interesting Piet's comments as hadnt really noticed the harshness in that range under 2900 but being old school always try to keep the engine revving .............the theory many moons ago before the real reasons for the bearing issues became apparent was that people were lugging the engines... so old school solution was dont lug it let it rev... I know that Vince commented to me the other day why I am always in a lower gear and letting the engine rev they feel oh so much better up around the red line when on song.
Interesting Piet's comments as hadnt really noticed the harshness in that range under 2900 but being old school always try to keep the engine revving .............the theory many moons ago before the real reasons for the bearing issues became apparent was that people were lugging the engines... so old school solution was dont lug it let it rev... I know that Vince commented to me the other day why I am always in a lower gear and letting the engine rev
they feel oh so much better up around the red line when on song.
R
Reggie3cl
Guest
Brett: Nothing like the vibes on your bike, no doubt. But then these old bangers are all different eh? What carbs are they- the tops don't look like mine.
Brett gone FCR Kehan mad,39mm set on the Cico and 34mm set on the RGS.I was whingeing about what I thought was clutch rattle in my bike as his bikes are really quiet, seems its Carby slide rattle and FCRs don't have it. He has made a great job of this having them fit with the standard airbox and still have access to the mixuter screws.One hell of a lot of work including the jetting, manafolds, and learning how to set them up,very tidy job.
Reggie, glad to hear you are on the way to sorting out your issue, yes none of these old bangers are exactly the same... ran the Cico yesterday arvo and it doesnt move its Dell's around much either so still weird about yours I guess maybe you mounts are crook as was thinking yesterday that when I worked in the UK was seeing different issues with rubber components etc than that what we would see down here. So now does anyone know a good source of new engine mount rubbers.. perhaps if we had enough old ones we could get some remade ( oil filled now that would be a challenge )
Vince is not quite right though while close no cigar They are downdraft Keihin's ... the Cico has FCR39's but the RGS are FCR35's ..both with custom made manifolds and angled inlet rubbers.. the RGS nearly got a set of Red's angled manifolds ( would have been better to get one of Red's complete set ups me thinks ) but I figured it out in the end.
I do have a set of FCR33's which measure near enough to 34mm in the bore and when I get some spare time will make up to suit one of the other bikes................think that may have been where young Vince got a little confused.
The exercise aint for the faint hearted let me tell you...
Vince is not quite right though while close no cigar
They are downdraft Keihin's ... the Cico has FCR39's but the RGS are FCR35's ..both with custom made manifolds and angled inlet rubbers.. the RGS nearly got a set of Red's angled manifolds ( would have been better to get one of Red's complete set ups me thinks ) but I figured it out in the end. I do have a set of FCR33's which measure near enough to 34mm in the bore and when I get some spare time will make up to suit one of the other bikes................think that may have been where young Vince got a little confused.
The exercise aint for the faint hearted let me tell you...
R
Reggie3cl
Guest
You should stick something up here about the conversions. FCRs have rollers on the slides don't they which cuts down on the chatter- perhaps a better quality carb?
Motalia has them at about 60 quid a pop (remanaufactured with stainless housing) so that would be 6 off then- eeek!
I've ordered up some Delrin and a basic cross sliding clamp thing for my pillar drill to make a simple milling machine so will knock out a couple of bearing blocks for the choke rod- should stop or at least slow down the wear on the carb bodies and keep the damage to the plungers to a minimum.
In my bike's defence, it has a very characterful engine- I don't know if this is because of the bigger pistons, but it ain't no turbine and that's OK with me.
Still, bloody old bikes....
Motalia has them at about 60 quid a pop (remanaufactured with stainless housing) so that would be 6 off then- eeek!
I've ordered up some Delrin and a basic cross sliding clamp thing for my pillar drill to make a simple milling machine so will knock out a couple of bearing blocks for the choke rod- should stop or at least slow down the wear on the carb bodies and keep the damage to the plungers to a minimum.
In my bike's defence, it has a very characterful engine- I don't know if this is because of the bigger pistons, but it ain't no turbine and that's OK with me.
Still, bloody old bikes....
Dellortoman
Hero member
- Location
- Tasmania, Australia
Reggie3cl said:
Sorry Reg, I didn't get back to you on this one ...
Top photo is Keith's attempt at a carby stay on a RGS (or is it an SFC1000?)
Bottom photo is my improved version on the 180 Jota. Obviously the 120 engine doesn't have a tacho cable to tie it to, so you'll have to come up with some other anchor point. Possibly an extended cam cover bolt.
Reason I did it is the weight of the carbs and pod filters hangs off the manifold rubbers with no support at the back end.
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piranha-bro2
Hero member
- Location
- Melbourne
Hey Brett, are you sure they're downdraft? They are usually fitted to Yamaha FZrs and R1s. Horizontal are a la Suzuki GSXR and what suit the Lavs.Brett said:
Do your FCRs have choke systems? or do you start using the accelerator pump method? Interested because I'm fitting 2 pairs of 39mm FCRs to my two SF-based motors and have faith that with no chokes, I can start with a couple of pump squirts (as brother Tippie has always done successfully on his).
Quentin
D
Davo
Guest
Was investigating a carb conversion on the Le Mans and have heard interesting reports about keihin FCR rollers giving up the ghost on Guzzi conversions and parts being sucked into the combustion chamber with undesirable results. Said to be due to the vibrations.