xu5m engine rebuild

The piston is cambered though. ie they aren't a cylinder. The largest diameter is about 2/3 of the way down. How would he know what they're supposed to be at the bottom of the skirt? Sounds suspect to me.

that's why I'm double checking everything here. so how do I know if my piston is fine to keep using? what should the size be?


Got the new fuel pump fitted today on my 1.6 project, going to do a few runs up and down the street first thing in the morning to bed in the rings then tuning on the 27th.
I have the pistons out of my engine available. You would need to change at least one of the rods though, destroyed by the run big end bearing. Callum did say that your engine was getting pretty tired Whoever installs the rods has to know what they doing, not to use too much heat.
Thanks. If my pistons need replacing I'll probably buy em and have fun driving the car around!
 

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Well, my project turned out not so well. The copper head gasket is leaking compression into the cooling system, apparently I should have used O-rings. This means that the spare XU9J4 has to be fixed as well, so at least I saved the disappointment of that not working. I am just going to put a standard head on the Si with a normal head gasket, should go fine with the GTi inlet and Megasquirt. Even before the gasket went the compression wasn't great according to the cranking speed. Probably needs over 11 to 1, I had around 10.8. Didn't go very well and I don't think this was all down to tuning.
 
I have found some bike carbs for my build. I'm buying them online so can't check them out in person. Is there anything I need to ask about before I get them and the intake manifold looks a lot more open to mine. will I be fine matching my head to the manifold when I get it or leave it alone?

The manifold is bogg bro's with R1 carbs and was previously on an 8v xu9 and they are £200 which seems reasonable.
 

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I have found some bike carbs for my build. I'm buying them online so can't check them out in person. Is there anything I need to ask about before I get them and the intake manifold looks a lot more open to mine. will I be fine matching my head to the manifold when I get it or leave it alone?

The manifold is bogg bro's with R1 carbs and was previously on an 8v xu9 and they are £200 which seems reasonable.

Permitting they are in ok condition you will be suprised how easy they are to get running. Being a constant velocity carb they are very forgiving. You could ask if current owner knows the main jet size? Some run a small main with air correctors blocked off and others run larger main jet and leave correctors. R1 are nearly 40mm bore so probley a tad big for a xu5 really. Even though you can jet them to suit the smaller engine your low end engine speed will suffer .
 
Permitting they are in ok condition you will be suprised how easy they are to get running. Being a constant velocity carb they are very forgiving. You could ask if current owner knows the main jet size? Some run a small main with air correctors blocked off and others run larger main jet and leave correctors. R1 are nearly 40mm bore so probley a tad big for a xu5 really. Even though you can jet them to suit the smaller engine your low end engine speed will suffer .

Good to know. thanks. I have asked the owner.

It looks like the carbs are missing the TPS but have asked the owner about that (do I need this for carbs? I dont know haha)
 
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If you get the geniune R1 tps or a replacement it just makes things easier as xu5m tps works opposite way. I made mine work as it stops the k light coming on the dash and it might help the system work better i never really investigated not having it work but i did test drive without it connected and it still drove fine. You can measure the output of the two tps and compared them then i used a resistor to make the bike tps send the ecu a signal very close to the xu5m output. They should be both 3 wire so very easy to do once you identify wires. A trim pot was on the cards but it was so close i left it as was.
 
If it was mine id shop for 36mm carbs. Even a pretty hot 2ltr motor running 45 webers will only run 36-38mm chokes. Bike carbs have no chokes so you will be getting the whole 40mm bore. Also forgot to mention regardless of which way you go carb size you will also need a efi to carb reg try searching for a malpassi fpr014.
 
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Even though you can jet them to suit the smaller engine your low end engine speed will suffer .

will it be worse than my standard si?

I will look more into that efi to carb reg you recommended as well so thanks for the recommendation.

I'll keep looking for other carb set ups for sale but might end up with these if nothing else pops up.
 
will it be worse than my standard si?

I will look more into that efi to carb reg you recommended as well so thanks for the recommendation.

I'll keep looking for other carb set ups for sale but might end up with these if nothing else pops up.

With the 40s it probley wont accelerate as quick as 36s until its screaming its head off.
 
here is my old setup
 

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i set my oil breather hoses up the same as the peugeot Grp A build manual shows. I sort off cheated and used my dipstick tube as the one in diagram thats marked 3 (19031-02
 

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Been a little while since an update.

Everything was slow to turn up with covid but all the parts arrived recently so I will get stuck into things when the snow starts to melt here in Canada. Ended up getting a decent amount of parts and Pug1off convinced me to get a 3j diff and 309 control arms (swapping to gti k frame) to get a bit of camber upfront.
The flywheel got cleaned up by the machinist and they took a bit of weight off. Does someone know what they are stock? it's 5.9kg now. The head is with the machinist getting cleaned up and new valve guides, skim etc.
I applied for collector status for the Si and it got accepted! Insurance is expensive here and it became a lot cheaper now it has collector plates.
 

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Winter is finally over in Canada so have free time to get this thing together.

I have started with cleaning up my gti k frame as I'll be putting that in. took a wire wheel to bits that needed a tidy then painted it along with my spare knuckles. I have a cut down L bracket, new shifter linkages ready to go with it and there will be 309 arms getting used for a bit of camber.
Shifting to the gti k frame means the drop links will fowl the brake line bracket of the si so what have others done abut that? cut it and bend it to another location or remove?

Diff is installed too but took a bit of massaging to clear in the gearbox. I have been cleaning the box so it can be painted and look neater but having trouble with all the crevices that have crud in em. what is the easiest method of cleaning em?
I have attached a picture but how do you remove the clutch fork? I want to be able to replace the bearing guide tube thing but can't figure out how to remove the pin that holds the control lever. Any idea?

The crank was easy to install. Bearings were all to spec and then I smothered them in assembly oils and tightened everything down. The hockey pucks went in relatively easy but stretched more than I thought they would. The end float was measured with a dial gauge (my first time using one) and was right in the middle.

Moving on to the pistons. The new liners all seem to have about the same protrusion so not worried about that but the rings are giving me a bit of confusion. All of the top rings are about .38 -.4mm and the second ring is larger at about .45mm. The Haynes manual I'm working from mentions the second gap being smaller .15 - .35mm so my numbers being different give me a bit of anxiety. The Haynes manual also talks about the second ring having a step (the ones that were in the car had the steps) but the one's I'm installing do not. Are the rings with out the steps going to be fine and what should I do about the ring gaps? I can give more detailed numbers on the ring gaps if needed.

Everything is coming along slowly but not really in a rush and it's fun learning all of this stuff. There are seals such as the speedo housing ones, thermostat and other things that I am missing but I have to order new shims for my head so will do that all in one go.
 

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bottom half is back together and looking pretty neat after it got a bit of paint. picking up the head in the next few days and ordering the missing parts once the shims needed for the cam have been measured.
 

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