[HOT 1200]

Over the years, many of you have posted some very good and interesting information relating to the humble 1200 engine.
The info is scattered all over the VZI forum, this thread enables 1200drivers to get together and share general info, 1200 tricks and anthing else 1200........strickly 1200. (OK 1200 big bore kit drivers are included here......:hug

GaV

 

[billybug]

OK a Quick 1200 Q for you

I have a Brosel Solex H30/31 carb on my 1200 and a 60's VW (not Bosch) Dizzy but at partial throttle and under load I get hesitation and misfiring - when I floor it its fine. I've tried swapping the Dizzy for an early 60's Bosch one - no better - and I've cleaned out the carb (not actually driven it since doing the carb) - any idea what could be happening?

Could it be I have the wrong Dizzy (these are vac advance only) and its not advancing properly at partial throttle? If this is the case any idea of the best Dizzy for this carb (Model no etc).

Or is it another problem?

 

[HOT 1200]

I would say first place to look is the pump jet on the carb....
Thats the little brass 'tap' that sits in the top of the carb...
When you operate the throttle, fuel should progressivley squirt from this tap....if they get blocked, it gives you massive flat spot and severe hesitation...
If its blocked up, the tap can be removed (simply pulls out with pliers once you have removed the top of the carb)....to clean, rod it with a either single strand of auto electric cable or fine steel wire (such as the type found on your wire brush!)
Then refit, make sure its all the way home and facing correctly down into the carb......then test again, if working correctly, your bug will now feel amazing!
GaV

 

[billybug]

I'll give that a go - I cleaned the carb and fuel suirts from it when I pull the throttle lever fast, but nothing when slow - I'll try again - hopefully that'll sort it! Cheers!

 

[HOT 1200]

They can get 'part' blocked by dirt......also worth checking the accelerator pump diaphram.......

And, as its a 'replacement carb', the fuel taps are normally too small, I drill my ones out to .7mm, that sorts out the flat spots and gives the engine a bit more vavaavooom.....!

GaV

 

[billybug]

Thing is before it was serviced it was running perfectly - I had it serviced (not by me and by serviced I mean new plugs, points, condensor, valve clearances checked and adjusted, new fuel filter, new Dizzy cap and rotor arm) and it was running shite, since then its had another distributor fitted, then removed again as didn't make any difference, points re-checked, new coil, plug leads, new fuel lines, the carb cleaned (didn't clean the jet out as you described tho) timing checked and re-checked, oil changed. I've even had the carb set up using an emissions analyser.

Also in addition to the weird misfire its now having trouble hot starting - never did before Also this problem only occurs when the cars hot and off the choke, when its cold and on choke its fine?

The only thing the guy who serviced it did to the carb is he said there was a problem with the choke butterfly staying open which he adjusted.

 

[billybug]

They can get 'part' blocked by dirt......also worth checking the accelerator pump diaphram.......

And, as its a 'replacement carb', the fuel taps are normally too small, I drill my ones out to .7mm, that sorts out the flat spots and gives the engine a bit more vavaavooom.....!

GaV

Wheres the fuel taps on the carb? Also is the accelerator pump diaphram the bit on the side?

Also the carb has only done 1800 miles

 

[HOT 1200]

Yes, pump diaphram is on side right hand side of carb.......
Fuel tap sit on top of carb (once you have removed the carb top) and looks like a small brass pipe, bent like a swan neck.....
Have you checked the timing.....?

 

[billybug]

I wish you lived closer to Bristol dude! I'd take my little 1200 to you for a 'spruce up '

 

[al_kaholik]

My 1200 tip? Stick with it - they are good motors. Practice heel and toe so that you can utilise what power there is. And full throttle is the only throttle

 

[DubKopfeYellow]

Mines quick enough for me sits at 70 (as long as theres no hills) so i'm happy, for now

 

[Bugsy_Malone 666]

i got a 1200 engine, then i turned it 1496cc :lol:

the 1970 crank case takes bigger barrels and pistons but its at that point that you notice pistons/barrels/pushrods/deflector tins/headtins/heads/manifolds are all very different.

but happily I have fitted 1600 conrods/pistons/barrels/heads(SP) to a 1200 bottom end although i have yet to start it up!

what sort of limit RPM was is the crank good for?

im thinking of sticking in one of those 4500rpm governors in so i dont break the 1200 crank.

 

[HOT 1200]

If you have fitted 1600 conrods, then the crank is not a 1200 crank.
13-1600 rods do not fit 1200 cranks...rods are too narrow.
BUT 1200 rods will fit a 13-1600 crank if you machine them, 1200 rods are too wide

1200 cranks are good to 5,000, mine often sees 5,500rpm.....they snap at anything over 6,000.......but flexing starts as low as 4,000rpm......
(if you flex them too much, metal fatique sets in and it may snap at tick over when you least expect it !!)
Bearing life on 1200 cranks often used above 4,500 is very short...expect less than 10,000 miles. The centre main wears on the sides but top to bottom remains untouched.......
If knew how to post pics, I have an excellent example.....

GaV

 

[Bugsy_Malone 666]

im positive its a 1200.

the heads were 1200, the pushrods were somewhere around 1/2-1" shorter! there is definatly several mm less throw. also the air deflector tins were several fins shorter than normal.

its a unit which was remanufactured at some point im wondering if its been ground different.the 1200 conrods were shorter and obviously has smaller gudeon pins.

im going to fit a governed rotor arm which limits it to 4500rpm so i dont break it, but looking at the specs in the haynes i have the power band is lower than a 1300/1600 anyway so i shouldnt need to rev it so hard.

 

[HOT 1200]

One way of telling what crank is fitted, is by looking at what exhaust fits the motor...
If you have a 13-1600 crank (69mm) then only a 13-1600 type exhaust will fit (because the engine is at least 10mm wider)

The lil 1200 crank (64mm stroke) is narrower, which is why all 1200 engines have to use a unique 1200 only exhaust.

My guess is its a 1200 motor with a big bore kit (83mm 1385cc kit??)
This is the only big bore kit currently available for 1200's which have unique pistons machined to accept the smaller 20mm wrist pins.
(all 13-1600 motors use 22mm wrist pins)

GaV

 

[Bugsy_Malone 666]

it `was` a 1200 when I got it, D code block, smaller conrods with smaller gudgeon pins, 1200 heads etc and 77mm pistons

but 1600 rods(from a fastback) fitted to the crank and being a later D code case 1600 pots fitted into the case, so then i fitted 1600 SP heads etc

one thing i did do was with the heads off on build up i used my vernier caliper to measure to stroke, which came out at 64mm

so basically im ending up with a 64mm crank 85.5mm pistons and stock length barrels resulting in slightly lower compression.

this could be a unique combination engine i have built

 

[HOT 1200]

I scratching my head, not sure how you managed to use 85.5 pistons and barrels with a 64mm crank ???

I did some sums......worked out that would give you a deck heigh of at least .250th
Thats a compression ratio of less than 5.25:1

Im surprised it 'starts'..........
Unless you had the barrels shortend / machined down ?

GaV

 

[Bugsy_Malone 666]

I scratching my head, not sure how you managed to use 85.5 pistons and barrels with a 64mm crank ???

I did some sums......worked out that would give you a deck heigh of at least .250th
Thats a compression ratio of less than 5.25:1

Im surprised it 'starts'..........
Unless you had the barrels shortend / machined down ?

GaV

I havent tried starting it yet :lol:

hmm nice low compression, just right for a long lifespan :lol: or a turbo!
or even TVO fuel

im just doing it for the giggle really, its built for the total sum of a gasket set all the rest are bits i had kicking about.

soon as i get the inlet manifold sorted we`ll see what happens

 

[HOT 1200]

Good Luck, let us know how it goes....
Ive got my vintage HOT 1200 to build this year.......
So far.......
1967 small bore 1200 case and entire bottom end
ERSON V300 cam (vintage early 70's cam!!)
1300 twin port heads
Twin Dellorto FRD 34's (baby dells)
but also have a twin Dellorto DRLA 36 kit (depends how brave I feel)
Not sure about pistons...
cant decide between 1192cc or 1385cc big bore kit.

GaV

 

[Darcy]

Good Luck, let us know how it goes....
Ive got my vintage HOT 1200 to build this year.......
So far.......
1967 small bore 1200 case and entire bottom end
ERSON V300 cam (vintage early 70's cam!!)
1300 twin port heads
Twin Dellorto FRD 34's (baby dells)
but also have a twin Dellorto DRLA 36 kit (depends how brave I feel)
Not sure about pistons...
cant decide between 1192cc or 1385cc big bore kit.

GaV

Be brave Gav - the force is with you .............:lol: