PDSIT issue

[fido]

I've been looking at a van of a forum meber of JustKampers forum as she has had all sorts of problems with her UK spec T25 2L aircooled van after a so-called "specialist" rebuilt her 2L aircooled engine.

Her problem was that it wouldnt idle and the top spped was about 40 mph. I said I'd go and have a look and at least go through a few simple things.

first thing I spotted was 3 inches of slack in the throttle cable, the linkage was very sloppy too with the roght hand ball socket missing the plastic socket in the linkage cross bar. These were simple to sort out of course.

Next was that the engine was shaking horrendously on idle. Its a hydraulic tappet engine, and presumable the idle was just so low, the tappets werent pumped up. The central idling "hole" was hardly pulling any air - again easy fix and a couple of turns of the nut (not a screw strangely on these) and she was hissing nicely and the speed picked up, but still with quite a shake (could hear the H/Xs hitting the mounting bar!!)

Timing was at 30 degrees at idle??? took both tubes off the dissy, and it was still bad - adjusted to 28-30 max advance - sits around 10 at idle with hoses off. Put retard hose on, and its at about 3 ATDC - OK. Put advance hose on and its at 25 BTDC. odd. lower idle speed, still have vacuum on advance line.

So have removed (temporarily) and blocked with screws both advance and retard lines and she is running around without these at the moment. Witht he lines on, the idle stabilizing unit is working overtime changing the idle timing, and this I think is part of the issue with the VERY wobbly engine. With hoses removed it revs fine and idles smoothly.

However, the top speed is still apparently around 50 mph. The distributor is advancing fine on the centrifugal advance, so this should be fine for 60-70. I'm thinking maybe fuel delivery is impaired? Maybe the engine has been damaged by running around in such a state previously. I'll do compression readings next time I go around.

I'd also like to set up the carbs properly. There should not be vacuum at idle above the throttle plate. I'm guessing the "engine Builder" has turned off the central idling circuit as much as possible and was trying to get a decent idle speed by using the throttle stop screws on the carbs. What is the right sort of base-setting for the throttle stops? Am I on the right lines here?

I get very angry when people get ripped off like this, and I'd like to get this sorted for her, as she is not a rich person, and it seems the builder is doing more damage than good.

I'll check the fuel lines, filter and rate of fuel supply too next time I go over it.

[fido]

just read Dave105's post and the replies... perhaps I should actually read the forum before posting
=D>

will go with the half turn, check and double check the fast idle isnt sticking on, and syncronise the carbs. then we'll see how things fare.

Thanks Dave105 for your reply on the JK forum :)

[Amskeptic]

just read Dave105's post and the replies... perhaps I should actually read the forum before posting
=D>

will go with the half turn, check and double check the fast idle isnt sticking on, and syncronise the carbs. then we'll see how things fare.

Thanks Dave105 for your reply on the JK forum :)

I am now monitoring this thread, and will be glad to assist as you report in. Restore her faith! If you continue to get advance signal with properly set stop screws, let me know. Sounds buggered up in there.
Colin

[fido]

OK.... here are the further findings...

reset all of the mixtures, idle stops etc as per the Colin guide on the samba. With the central idling curcuit off, idle rpm was 500, and with it back on 850. Bypassed the "idle stabilisation unit". With retard line on, timing is 5 ATDC as it should be. BUT when rpm increases, the retard line doesnt let go. The advance line also doesnt die off at idle (despite all attempts to stop this - tried having less air going through the carbs and more through central idling circuit etc. Gave up. removed both vac lines. Its at 7 degrees BTDC at idle, and goes to 29 BTDC max rpm. At least the centrifugal advance is fine!

I noticed when I removed the crankcase breather (to remove the airilfter to balance carbs) that there was ALOT of air coming out of there. Indeed, the RPM at idle goes down about 200 rpm when I take the breather off the airfilter box! (mild turbo charging??!!)... There was also alot of oil swimming in the bottom of the air filter box and the filter itself was dripping. I immediately thought this must be rings... But on a warm engine the compression readings are 160 for 1-3 and 170 for no.4 (bit high? Maybe no head gasket and no shim to compensate?)..

So, we have excessive pressure in the crankcase, but compression is excellent. Only other place it could come through is guides. Would badly adjusted hydraulic tappets cause this? I can reset them next time I visit (tomorrow), and I will also change HT leads and plugs (though I'm sure this wont make any difference).

Where do I go from here?

[fido]

anyone?

I'm beyond understanding this. Guess the engine must have been built to 10:1 CR or something daft.

The fuel pump has now been replaced by the garage who did the rebuild, as she broke down due to lack of fuel delivery. I'm hoping that it was a split diaphragm, petrol in engine, and alot of this was boil-off. However, it didnt stick noticably of petrol, so maybe I'm hoping a little too much here. I spoke to the engine builder, and he freely admitted he worked pretty much only on type 1's and didnt have much experience of type 4's (so why did he rebuild the damn thing then !!!! rather than buying a recon for her for £1400 and fitting it!..

[RSorak 71Westy]

The only way an engine can have too much crankcase pressure is blowby past the rings.....

[Dave105]

Hi Fido

Been reading your thread with interest, as you know been fighting the same battle as you for the past 6 months or so, to say these carbs have a steep learning curve is a bit of an understatment! Im no expert on these things but the retard signal certainly is strange. The takeoff for this is the nipple on the inboard side of the carb, it takes its feed from a hole that lies just below the throttle plate when its in the closed position. at least thats where it should be, the only way to alter this is by the throttle stop screws. I found these very difficult to adjust on the van as its dificult to see whats happening. I ended up painting tipex behind the screw stop so I could see the gap better when backing out the stop screw.
The retard signal should disappear as soon as the throttle plate moves. this in turn uncovers the advance hole (on the other side of the carb and covered by the throttle plate at idle) On mine I set up 2 vac gauges, one on retardand one on advance. Thats how I found the advance was staying on at idle (due to an incorectly set up choke. have you tryied wedging the choke fully open to see if this is the problem (a peg did the job for me)
'
make sure that your throttle linkage isn,t holding your throttle open after youve set the gap. Took me a while to syncronise my throttle positions AND get them both in the right position (still think mine are a tad too open as my idle with central idle disconected `is still about 800ish) so check your throtle position with everything connected.

Not sure how excessive crank case pressure could find its way back into the carb

all I can say is keep at it and you should get there eventually. Where abouts in UK are you?

Dave

[fido]

Two problems were at fault: excessively worn valve guides being one, possibly caused by completely out of adjustment tappets (and hydraulic to boot - yes, you do need to set them properly!!!)...

So, drives fine now, but the crankcase pressure is still high. New guides need (heads probably - who knows what shape the valve seats will be in).