DERESTRICTING GUIDE
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@connorjordan185 It sounds like you have another problem dude, go through this list and check each point;
- Is the PV adjusted and performing correctly?
- Check Spark plug cap and HT lead for any faults?
- Is the coil in good order, are you getting a good spark?
- Are any of the jets blocked?
- Are there any blockages/leakages/worn pipes etc in the air flow system/inlet manifold, or is the air filter clogged up?
- What is the engines compression, have you checked it?
- Any loose nuts/bolts on cylinder head?
- Is the Head gasket OK?
- Is the cylinder head warped?
- Any loose joints/seals or holes in your exhaust system?
I would check all of those and see what any of those show. If they are all good then you may have a worn piston, rings, or cylinder? Or your crankshaft oil seals may have gone? But a compression test will give you an idea of what condition your bottom end is in???
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@NINJA thanks mate, I will go through everything on the list, but my bike did have a full engine rebuild just before I bought it, and since then it's had 1 piston, then it overheated due to a broken thermostat which warped the head, so the head got skimmed and a new piston fitted while it was in bits. So I believe the engine to be in ahright nick, even so I did do a compression test last week and come back between 90 and 100? If this was a car I would be worried but I believe it should be around this figure I just couldn't find an exact figure
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@connorjordan185 A 90-100psi compression is on the low side, 2 stroke engines normally run higher at 120psi+, the optimal compression range should be between 120-140psi, which is the most common range with these bikes. It sounds like you either have a leak in the air flow system, or damaged reeds? Or a dirty carb/partially blocked jets or one or more of the engine seals have gone? Which is the most likely culprit, as the crankshaft seals are usually the first to go.
How many miles has it done since your last rebuild? Did you 'run in' the new piston? Your overheating problem may have also damaged the piston rings, hence the low compression. You have lots of area's to look for faults, it's just a process of elimination until you find the culprit???
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@connorjordan185 Your welcome!!!
Here’s a great tip for you, do 3-5 compression tests and record the results. Then squirt some oil, about a teaspoon's worth, into the cylinder through the spark plug hole. Now re-run the same amount of tests again. Adding the oil will hold compression for several turns of the engine. If your retest with oil gives a higher compression test result, you will know the rings are worn. If there is no change in compression, it's most likely a worn engine seal?
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@NINJA thank you mate I will give that a go tomorrow, I have been through the carb, checked the reed valves and cleaned everything out with brake cleaner then the air line. I found a bare wire that had been nipped exposing copper. It was one of 2 wires coming from the coil, I thought I'd found the problem until I finished and quickly learned on my way home that there's no difference atall, nits so confusing as a few days ago I was on it and downhill it was fine, it was actually screaming how it should, but I have tried it downhill since then with no luck and a max rpm of about 6-7000rpm
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@connorjordan185 Your welcome, do the tests as I have suggested and see what results you get? But is sounds like you have a deeper problem than just 'something is restricting you'.
