40 replies to this topic

[Trissy B]

Hi all, have a 1275 with an Hif44, Mg metro cam. Its been off the road for 6 weeks and running fine before..

I've put on a new maniflow stage 2 lcb and rcm exhaust. Also the carbs just been modified and inlet manifold port matched.

Now, I had trouble initially starting up eventually getting going with full choke and no throttle. It idles erratically but the main thing is that any throttle kills the engine. Tried mucking about with the mixture but can't get it right.

Any tips?

[Jamdog]

Check you've put all the hoses back on. Vacuum pipe to inlet manifold, breather hose to carb. They can cause it to run rough. Refill the dashpot oil as its probably come out when you took the carb off. 

 

If that doesn't work, you'll have to start at the beginning - check each spark plug is firing, then check timing etc etc

[andyapanel]

Check the carb piston can move

Good luck

[dyshipfakta]

Fuellings out needs a new needle or an air leak somewhere

[Trissy B]

Hi, thanks for comments. Just made some progress and it now idles without choke (just, but still is all over the place changing from 500-1500 rpm, hardly ever nicely at rest) and now allows you to blip the throttle and rev up, but then nearly dies straight after. 

 

Process:

 

- Initially set the jet to 2mm below the carb bridge (this was way out at 9mm below before, too lean?),

- Increased idle speed (again this was way out) and richened enough to take of choke (clockwise on the mix screw).

- Richened a bit more to allow me to reduce the idle speed down to 800-1000 rpm average.

- Still has symptoms of the above.

 

Checks done:

 

- Sparking on all cylinders (check change plug leads on/off)

- Vac pipe is working (check change on/off)

- The timing seems ok - 8deg at 1000rpm and 16deg at 2000rpm (vac off)

- Breather is on (check change on/off)

- Check inlet manifold seal (spray wd40 in area and no change in revs)

- Dizzy cap ok

- Checked the needle - BDL

- Carb piston moves up and down

- Carb oil is the SU oil

- Used the pin to raise the damper and it didn't seem to make a massive difference to be honest.

 

Please shout with any ideas of anything i've done wrong/ haven't done! Obviously need to get it on a rolling road but need to drive it there!

 

Do you think BDL is the wrong needle? Haven't checked the carb spring, how do i get to it to check?

 

Going to order a colourtune tonight, do i need the 14mm version?

 

Totally rubbish at this - usually rely on my dad for this stuff!!  

[croc7]

Having done all of those checks, it sounds to me like you have a mixture problem. Have you checked the operation/mechanism of the mixture control?  Check that the bi-metallic temp compensator inside the float chamber was (is) properly connected to the jet.  To do this, you will have to remove the carb.  Index the float cover to the carb body, then remove the float cover to check.  You may as well check the float level dimension while you're there, should be .040" +/- .020"  The mixture control snaps into a recess on the jet.  I disabled mine by cutting off the bi-metallic pieces on either side of the compensator, which I guess makes it no longer a compensator, just a jet height (and therefore) mixture adjuster.  Make sense?  If you do this, you aren't chasing the mixture as altered by the bi-metallic temp compensator as you adjust the mixture control. I use a BDK needle on a warmed up 1360 with all of the usual improvements.  Red spring.  To get to the spring, remove the three screws holding the dashpot and pull the assembly out of the carb, being careful with the needle.  Then to get to the spring, I remove the needle to prevent possibly bending it, support the piston from below, remove the circlip at the top of the tube (where you fill the damper oil) and separate the two.  A bit verbose, hope it helps.

Edited by croc7, 03 June 2019 - 08:41 PM.

[carbon]

Hi all, have a 1275 with an Hif44, Mg metro cam. Its been off the road for 6 weeks and running fine before..

I've put on a new maniflow stage 2 lcb and rcm exhaust. Also the carbs just been modified and inlet manifold port matched.

Now, I had trouble initially starting up eventually getting going with full choke and no throttle. It idles erratically but the main thing is that any throttle kills the engine. Tried mucking about with the mixture but can't get it right.

Any tips?

You have put on a new maniflow stage 2 lcb, it is likely the flanges on this are 8mm thick.

 

Some of the inlet manifold flanges are not quite 8mm thick. In my experience the washers can't take up more than about 10thou difference between inlet and exhaust flanges before you start to get poor sealing on inlet and idle / weak mixture issues.

[cal844]

Poor mixture or no or too thin dashpot oil, try a 10/40 or 20/50 oil in there

[postve]

@trissy B

 

Wow, I have the similar same issue but mine runs fine and I do not have the vacuum advance hooked up. 

 

Issue is similar that accelerating under 4K or so she does well but as soon as I put a lot of load, she dies and comes to a halt. I did notice I could push a few times but eventually she dies out - running a little lean as pops at higher revs.

 

Interestingly enough, on the road, last time I popped off the dashpot, took out the piston, dropped it back in, she fired right up?????  Cannot figure that out for the life of me.

 

Going to test again tonight as checked everything including the float by an expert over on my side of the pond;

 

- 1275  - with BP255 CAM added

- Fletcher LCB exhaust

- upgraded from HS2' to HIF44 - from Metro 

- Had a BFY/BES - needle - same issue, dropping in a BDL tonight

- 0.130 for needle depth - plan to increase mixture as popping whenever I did get above 4K

- Petronix electronic dizzy

- Petronix coil

- New starter solenoid

- new ignition switch

- new plugs - looked a little lean first time out and as I adjusted mixture/idle - showing as brownish so this is ok (although it does pop as mentioned at higher revs if I can get er there)

- Valve clearance will check once I hit 500 KLM on new BP255 - only done about 100

 

I basically checked everything I can think of and still cannot figure out it dying at higher RPM???

 

Help - anyone!!

[croc7]

Air filter?

[cal844]

Air filter does sound restrictive, I have my mixture set so they're a dry black soot. The cars run very well indeed

[postve]

Thx for the reply and I don't think so as I have k&n filters which I cleaned and oiled before installing the HIF44. Now, one bone head move I did was spray the cleaner on and totally forgot about it and it dried - overnight.

I kicked myself the next morning and washed it out thoroughly sprayed and oiled properly- not sure if that could be the problem but really do not want to spend another $100 to replace.

[postve]

As a side note I fired it up last night, too late to drive as the Raptors game was on, she idles amazingly, no pops, etc, and I out back in the BFY needle as want the richness and maximize torque acceleration etc.

I suspect the problem is still there so reaching out to you fellas early so I can catch some more feedback when I get home and really test it again.

Still scratching my head on it dying upon hard acceleration, then removing dashpot and piston, putting back in and she fires up like nothing every happened - 10 minutes Jonathan the side of the road - weird

[andyapanel]

Have you cleaned the inside of the dashpot (where the spring and piston sit)?

If it is manky, the piston can stick. I know, because it was my first mini issue...the first of many :)

[postve]

Thx Andy and good suggestion but I am thinking not the issue as I failed to
Mention HIF44 is refurbished and piston moves precisely as the manual mentioned and float is set correctly, had my local SU expert check.

But even he is baffled by the issue and of note it basically sounds starved for fuel when I accelerate hard. So, here is my plan tonight,

I keep reading about using 20/50 as opposed to usual SU oil - so I pulled dashpot and piston and filled this morning

I think that since viscosity of oil increases the richness upon acceleration, this maybe and just maybe might offset the starvation upon heavy acceleration

I have my BFY in and setting depth to 0.125 inches

She idles amazingly as I mentioned brown plugs and no popping etc.

One thing I did notice, I added Su oil last night, pushed in needle on had piston pipe pop out the top and filled her up. This morning when I went to empty and replace with 20/50 , very little came out?

Strange