Bypass tube replacement

[HQentity]

Hiya guys!

I have a week off coming up, and hopefully if the weather is good I'm going to take off the manifold and sort out my leaking bypass tube. I have the manifold gaskets, the bypass tube and washers, and from memory, a few pump housing gaskets. I'm gonna make the most of draining the coolant and take the radiator off and flush it through.

Basically is there anything else that would be worth looking at or doing while everything is drained and dismantled? Many thanks!

[sprint95m]

You need the O-ring for the inlet manifold.
Possibly a new washer for the engine block drain plug.

Check your gaskets line up properly....
from experience, the holes for the bolts and also the top right hole on the RH gasket need realigning.



Ian.

[dursley92]

It can be awkward to hold the manifold in place when you are lining up the bolts so a good trick is to use a couple of old sawn-off bolts as a temporary locating tool.

[geeksteve]

It can be awkward to hold the manifold in place when you are lining up the bolts so a good trick is to use a couple of old sawn-off bolts as a temporary locating tool.

Why have I never thought of that..

[MIG Wielder]

I think it would also be worth having the thermostat outlet elbow off.
You can then do 4 things.
1. If the bolts snap off it is a lot easier to get then drilled out and replaced off the car.
2. You can check the mating surfaces of the manifold/ elbow and clean them up.
3.You can replace the gasket.
4. You can check the correct thermostat is fitted and by suspending it in a pan of water you can check the opening temp is roughly right.
And while the manifold and water-pump cover are both off it is worth cleaning up the sealing surfaces where the bypass tube locates and seals. ( I use a Dremel with a wire brush. )
Tony.

[HQentity]

Thanks for all the ideas guys

Everything has been done, but I have one small problem, the engine revs are off the charts!

Whenever I push the throttle, the revs jump up and stay there regardless of the throttle position. I had a look at the throttle linkage to start with, just in case something had gone a bit wrong and it was jamming, but everything was fine. I've tried tightening the manifold to the head as much as I can but it doesn't seem to have effected anything. It looks very flush with the body, the gaskets were alright, one was a bit thicker than the other. I used a little gasket sealant too. I removed the whole thing as one part. I used some wd40 to clean the manifold face up and got some in the inlets, but I've run the engine a good 5 minutes at the 1500 or so revs.

When I pull the choke out nothing happens, until its a good inch out, then as it floods the revs drop, and runs like crap. When I put the choke back the revs climb back to wherever I revved to. If I switch off though, the whole process restarts and she opens at 1600 or so. When the cars hot though, the revs don't seem to jam as much, they fall back down to 2000 or so.

I feel like theres an air leak, I've tried adjusting the mixture a few flats each way but nothing immediately changed, I'm just worried tipping the carbs has caused something to stick? Anything I should be looking at in there? I'm stumped if I'm honest, I haven't touched the revs at all. The idle screw has always had to be almost completely up ever since I've had the car, and I've only recently got anywhere with the mixture.

Any ideas greatly appreciated!

[Jon Tilson]

Have a look at the wiki SU carb tuning guide. Make sure your throttle butterflies are returning to the shut position.

Jonners

[Mahesh]

Almost sounds like you have turned the throttle lever & spindle when the carbs were off the car, and the
choke link is jammed.

There are some good pics on the forum, (james467, carmine sprint) do a quick comparison, or put up a
couple of pics showing both your carb linkage sides and down to the jets.

Did you take the Jet linking lever off ?

[AlanH]

Undo the linkages and see if the revs drop.

[HQentity]

Mahesh, I think you may be on to something there! I had a look through James467's posts and found the pictures, it does look to me as if the choke isn't the same as his. I wanted to get some pictures up quickly this morning before I started though.

I'm reasonably confident the throttle is fine, I've had the spindle detached already and it moves very freely anyway. The choke linkage however is a bit gunky. Also I know theres supposed to be a gap between the screw and cam, but is the cam supposed to be rotated as far round as that? The screw could go clean underneath it, let alone touch it!!







Had a nasty fright yesterday when one of the fuel chambers somehow emptied all its fuel all over me as well, but through adjusting the mixture (I reset them both to maybe 10 flats), I've managed to get some sense out of the carbs, now starts (still without choke) at maybe 1300 revs, and doesn't seem to be sticking with the high revs now which is good. Some progress at least! Also I'm pretty confident theres no air leaks, covered the head in wd-40 and nothing happened.

[HQentity]

I think I'm there! just spent a couple hours rebalancing the carbs, and everything sounds like its running well now. Going for a test drive shortly

[Mahesh]

I just took a couple of pics for you,

20160505_113838_1462444953598.jpg (324.49 KiB) Viewed 889 times

20160505_113851_1462444953793.jpg (312.54 KiB) Viewed 889 times

[HQentity]

My god, its spotless! haha! Why is it our fast idle screws are different ways round? James's are your way round too?

[Toledo Man]

The Sprint has HS6 carbs which are different to the HS4s that the 1850 has. I was having idle problems last month which was documented in my resto thread so the photos I took might be of help. If not then I can take photos of mine from the same angle as yours.

[Jon Tilson]

Also Mahesh's HS6's are the later type with concentric return springs on the spindle rather than the earlier type with the
separate return springs that you have.

Looks to me that you choke is a bit misadjusted. You should have the cam a bit closer to the fast idle so it moves the fast idle screws
before pushing the jet down. I think on yours the jet would move down before the cam reaches the fast idle screw.

It also looked in one of your pics like the throttle forks arent quite in synch and one is holding the from carb throttle open a little.
It only needs a little to cause a big increase in idle speed. Loosen the clamps on both so you can control the idle speed only with the
screw and get them both sucking the same with a tube in your ear and listening at the exact same spot on each carb.

Its also pointless fiddling with mixture until the car is thoroughly warmed up.

Jonners