Leak down tests

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megawatt
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Leak down tests

#1 Post by megawatt » Tue Mar 13, 2018 1:48 pm

Just completed leak down tests on my spare GSX1100 EFE engine. All went well on cylinders 2,3&4.Unfortunately cylinder 1 was indicating 25%leakdown. OK for a road car, but not for a race bike. I'll check the inlet valve clearances, just in case, but it looks like the head will need to come off.
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Re: Leak down tests

#2 Post by Westbeef » Tue Mar 13, 2018 2:02 pm

Is this type of test better than a compression test or are the results generally similar? What's the plan, to correct it?
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Re: Leak down tests

#3 Post by megawatt » Tue Mar 13, 2018 2:28 pm

Compression test doesn't tell you where gas is leaking from combustion chamber. Leakdown tester puts compressed air into the chamber. You can hear where the leaks are from, either exhaust pipe, carbs/injectors or engine breather for leaking piston rings. It also gives you a percentage leakdown. Only £20 on eBay. But you will need a compressed air supply.
Next step is check valve clearances, then probably remove cylinder head and lap valves in.
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Re: Leak down tests

#4 Post by megawatt » Tue Mar 13, 2018 3:13 pm

Just checked valve clearances. Nothing excessive indicating possible bent valves. Most of em too tight indicating possible burnt exhaust valves. Think the head will be coming off tomorrow.
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Re: Leak down tests

#5 Post by Bianco2564 » Tue Mar 13, 2018 7:52 pm

On the gauges,the left hand is the supply pressure,its only 2 bar?

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Re: Leak down tests

#6 Post by megawatt » Tue Mar 13, 2018 10:55 pm

Yep. Before connecting to engine, increase pressure until gauge reads zero in SET area, then connect to engine. It's pretty obvious when there's a lot of leakage.
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Re: Leak down tests

#7 Post by SlowBusa » Tue Mar 13, 2018 11:13 pm

What Price range was the compressor you bought @megawatt ?

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megawatt
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Re: Leak down tests

#8 Post by megawatt » Tue Mar 13, 2018 11:19 pm

£120 from Lidl, with 50litre tank and 3 year warranty.
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Re: Leak down tests

#9 Post by Bianco2564 » Wed Mar 14, 2018 2:32 pm

megawatt wrote:
Tue Mar 13, 2018 10:55 pm
Yep. Before connecting to engine, increase pressure until gauge reads zero in SET area, then connect to engine. It's pretty obvious when there's a lot of leakage.
What inlet pressure does your set recommend?
On our Snap On set we use airline pressure in the shop,about 6bar.

Yes very good at diagnosing where any issues lie.

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Re: Leak down tests

#10 Post by megawatt » Wed Mar 14, 2018 5:18 pm

I'll have a look tomorrow mate, destructions are in the garage
Got the head off today. No signs of bent valves, but pouring petrol down the inlet ports shows leakage past the valves on No. 1 combustion chamber and very good sealing on the others. I'll remove the valves tomorrow for some straightness checks and lapping.
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Re: Leak down tests

#11 Post by SlowBusa » Wed Mar 14, 2018 8:12 pm

megawatt wrote:
Wed Mar 14, 2018 5:18 pm
I'll have a look tomorrow mate, destructions are in the garage
Got the head off today. No signs of bent valves, but pouring petrol down the inlet ports shows leakage past the valves on No. 1 combustion chamber and very good sealing on the others. I'll remove the valves tomorrow for some straightness checks and lapping.
Hopefully a Quick Fix then :D

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Re: Leak down tests

#12 Post by megawatt » Wed Mar 14, 2018 8:23 pm

Hope so. The ET motor had 60% on 3 cylinders.
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