180 in 120 frame

[Rufustbear]

Whats needed size of any spacers etc any info what so ever,save me hours of setting up time,has it been done before ?,cheers Rufus

 

[Grant]

Isn't there a difference in front mounting lugs between a series 1 and a series 2 180?
I think later series 2 had a similar lug to the 120s, just not drilled, or am I dreaming it?  :-\

 

[jotacorsa]

wouldn't the easy way be to rephase the crank?

i do believe grant is correct that only the series II
have the necessary front bosses for fitting into a 120
and utilizing the 120 mounts

if memory serves
the lower rear 120 mount stud goes through the lower rear case holes
and the bottom threaded studs locate in the frame as a 180
so it should be fairly easy to set any 180 into the 120
correctly positioned to do any mount fabricating

cheers,
scott

 

[laverdakeith]

The series 2 cases have the cast boss to accept the two front rubber mounts on the front of the case altho' it is undrilled and drilling the mounting holes is not realy a Black and Decker job, everything else is the same and an alternative front mounting system for a series 1 motor would not be too tricky to fabricate.
Do you intend retaining the rubber mounts Ray ?

    Keith

 

[Grant]

I thought the mounting studs underneath the 180 engine would be supefluous as there were no equivalents lugs on a 120 frame.
I recall the 120 engine being suspended on 6 rubbers.
2 at the front, 2 at the top back and 2 at the lower back only.

I may be wrong, but something tells me there are no lugs under the engine on a 120 frame.

 

[Rufustbear]

Ok this what i have one 120 frame and one 180 1200 moter  which i built at Ralph Allens last Xmas,i intend to race at Magny corr and spa next year so any advice will save me alot of time,would it be wise to have the engine half rubber mounted and half solid ?,one of the main reasons for this build is the the 120 frame handles better than the 180 frame again any help is greatly appreciated ,Cheers Ray,are there any engine mounting points that one could work off to mount fabicate the rest,Keith if nessicary will get frame up to you for any welding

 

[laverdakeith]

I would be inclined to solidly mount the engine Ray the 180 motor with its straight up and down vibration characteristics may give the rubber mounts a hard time, especialy the front pair, as they are being subjected to a different load than they were designed for. Is it an RG frame or a 120 jota type?

   Keith.

 

[Rufustbear]

Keith have added to my preivous post,the frame is stamped RGS if thats any help

 

[laverdakeith]

  If you have original RGS rear mounts they can be used to temporarily position the motor and use a bit of wood to choc the front up, best to get the proper mounts sorted first tho' you can be sure of where you are then. Give me a bell if you want, working today anyways........


    Keith.

 

[Jota Rob]

Ray

You might want to consider from a handling perspective, that making the engine a stressed part of the frame will give better handling than rubber mounting it. Thats not fact from my part but its the assumption I'd be working to if I was conceiving your project.. Which sounds very interesting !

Rigid mounting would probably give a more profound difference on a Double cradle  Laverda frame than a race frame or Motodd which has a more advanced construction. The spine of your RGS is clearly a better job, but the cradle is not much different than an old clonker 180 

Rob

 

[CLEMTOG]

This is dead easy,
Just cut six pieces of inch and a half (not two inch now, much too heavy) angle iron, eight inches long, drill a hole at one end, then bolt your six bits of angle to the engine mounting holes, then drop the motor into the chassis, warm up the ends of the angle and "curl" them around the chassis, get out your SIP 140 (remember to change the 13 amp fuse for a bit of 8mm rod), then  weld the angle where it touches the chassis, trim the excess off with a ?9.99 Red Devill 115mm angle grinder and you are hot to trot. Next just clean up the welds a bit, removing any bunches of grapes, if you see any tramlines in the welds,just tell whoever asks that it is "rail road spec welding" and then fill them  with Isopon (just like the Japs do and THAT is not a joke).Dont worry if the rear drive chain is not in line as Andy chain, does realy good quality zed shaped chains, they even have X rings.
CLEM

ps, if the angle does not touch the chassis, you can go down to your welding supplies and ask for some "prairie rods" they are realy good at filling up wide open spaces.(guess who got sent to the stores for that on day 10 of his welding aprenticeship, after cutting and tacking a bit too wide)

 

[Tom Eatman]

Hi guys, this is one of the issues that came up whenI got my Spaceframe kit a couple years ago. The frame is for a 180 engine and I had planned on using a 120 setup as for a race bike I prefer a left hand shift set-up. The kit was offered either way but something got lost in translation, not that it matters. I learned that the 120 and 180 cases are slightly different as far as the rear mounting points go and the front is obviously different. Everything I've read from Laverda's experiments with 120 engines in solidly mounted frames didn't fare too well with many cracked frames has led me to go the route of a rephased crank (180, thanks to Piet by the way) and modifying the frame for the 120 cases to be solidly mounted. My 1981 second series 180 Jota with solid mounts works great though I have read the 120 rubber mounted engines with the same frame tended to wobble. I would think there was a bit of method to the madness as the RGS and later frames are quite a bit stronger.

Tom

 

[sfcpiet]

My 1981 second series 180 Jota with solid mounts works great though I have read the 120 rubber mounted engines with the same frame tended to wobble.

Tom, Ray,

I have yet to come across a 120 Jota that tracks decently.... apparently the factory compromised the handling of the basically 3C frame by flexibly mounting the engine, removing any stiffness the engine may have afforded.  The engine mounts of the 120 Jota don't brace the frame in the manner they do on the RGS types.

Don't see any issues in solidly mounting an engine to the RGS frame either.  I would add the lower mounting point as well, the layout of the cradles is similar to the 3C frame and will benefit from any lateral bracing along the way.

Will have to wait and see how the different vibe characteristics of the 180 affect the RGS frame .

I have gone the other route, ie. (rephased)120 into 180 frame, dead easy.  One front lug needs drilling, the lowers need drilling and tapping.

piet

 

[phil37]

Hi Ray - We built a "Jota 150" as we called it - with a S1 180 motor in a 120 Jota frame ( We needed the 120 motor for a special). We mounted a central aluminium block - with the same holes and positioning as the Laverda 120 motor - this was screwed to the crankcases by some countersunk allen screws - obviously neccessitating the stripping of the motor. The only other mods required in order to use the original Laverda rubbers was to remove a small amount from a rear stud boss to enable fitment of the lower mount and drill a hole to locate the top mounting's locking arm. The breather assemly may need to be fitted with the outlet towards front of motor. Customer loved his "Jota 150" - even blasted it round Goodwood a few times at a very respectable rate.- Regards - Phil

 

[Rufustbear]

Many thanks chaps going a dry run/set up this week end ,let u know.Ray

 

[Scrumpy]

I believe this is the rear upper 120 Jota mount Phil is discussing. The series 1 crankcase has not been drilled to accept the locating bolt when the mount pivots around further.

Scrumpy

 

[1946kent]

Last year to the President meeting in Holland we vent for a short visit to VanDijks to see his shop and buy some parts and he was working on a frame,
He use some small rubbermountings and modify the frame many places.