Blocked main jet 200t

[spudulike]

The problem with the very informative threads on the forum is that everyone gets carried away into thinking they have serious problems and have to do their crank bearings and seals, when in fact they seldom give trouble, and problems are often very simple things, usually only carburation.

 

Very slight air leaks are acceptable, during a test the vacuum should be tested at no more than 0.5 bar and rise to no less than 0.3 bar in 20 seconds. The pressure test should be done at no more than 0.5bar and need only hold constant for 20 seconds.

 

Using higher pressure or vac may induce leakage that looks severe but is in fact within limits.

 

When you think of it a 32cc engine at WOT is moving over 400 litres of air every minute. A very small leak makes no difference.

 

Keep it simple guys.

 

I sort of....know where you are coming from but I have found so many issues when doing pressure & vacuum testing that I think they are VERY valid checks and have probably saved many machines.

 

The thing with air leaks is that if you have a slight one and the carb is set a little rich and the fuel oil mix is good, the engine may run fine for a long long time with no perceivable running issues.

 

The issue is if the carb is set a tad lean or the fuel is a few weeks old AND you have an air leak then POP, the machine is far more likely to fail.

 

Not sure about others but I have had a number of saws in, predominantly Stihls that still have their limit screws in place and have been serviced and on taching, have had to pull the H cap as the saw is over revving on the Stihl Max revs Spec. I guess Stihl set saws a little lean and as they bed in, they run higher and higher revs!

 

I think that if one of these saws running close to more than max spec revs then gets a bit of an air leak or has a bit of suspect fuel then it is much more likely to fail.

 

The other thing is a small air leak is a sign of a potential big one happening in the near future.

 

I know you can get hung up on this sort of stuff, heck some people run their saws with small air leaks without noticing that it has one so GK is sort of right with some guys getting hung up on leaks but I have found on some MS200s, if you push the crank around, you can make it leak down to zero in two seconds but left as is, it will take a minute and pass the 20 second rule. The point is that it will only leak once running and with a bit of chain pressure on the crank shaft.

 

The last repair I did potentially saved a 3120 from smoking it's new P&C kit, a seal was actually rotating in its seat and it had a real BAD leak.

 

So.......don't always grasp at the worst case but my opinion - passed pressure and vac tests give solid foundations that the issues on an engine are elsewhere.

 

Sorry GK - just my opinion but do look at general condition and age of the saw as well:blushing:

[spudulike]

Having a 200t that you know works would be great in this instance, just a process of elimination swapping parts on the poorly saw until it works! Haha I made the assumption that the copy carb would be ok to use, going on the quality of the existing zama unit...

 

And I was also dead set that the old carb was knackered, so when I found a split in the impulse line I didn't think about putting it back on (after it still ran like crap)

 

Thanks for the input everyone, I can confirm that the saw runs well! (Thank God)

 

The important thing is you have learnt a fair bit in doing this repair and that is worth the outlay:thumbup: