M@1 Posted July 12, 2007 Share Posted July 12, 2007 I've got a Thunder Tiger TS4N with the stock .12 engine and it's got a really annoying problem with air bubbles getting into the fuel pipe. I've set it to run really rich and it does so for about 50% of the time and the rest of the time it runs very lean. For example I will accelerate from a standstill and it will bog down and move with lots of smoke pouring out (as expected), I then stop, turn around and do the same and there will be no smoke at all and it will scream and sometimes cut out when it picks up speed. The engine gets very hot which I assume is as a result of it not getting enough fuel. I have checked over it countless time and have found nothing wrong with it, the pipes and tank make an air tight seal and nothing seams to be leaking or anything like that. One thing to note is that when I first noticed the problem I found that one of the engine head bolts had the thread stripped and fuel was leaking out of the top of the head. I tapped a new thread and put a new bolt in which has stopped fuel from leaking out but has not stopped the problem with the air in the pipe. Hopefully someone will be able help me, thanks for reading Quote Link to comment Share on other sites More sharing options...
cew27 Posted July 12, 2007 Share Posted July 12, 2007 try filling the tank up to the brim and see if bubbles go away if so leaking fuel tank Quote Link to comment Share on other sites More sharing options...
Samari Posted July 12, 2007 Share Posted July 12, 2007 Have you checked the carb and bearings for air leaks? Quote Link to comment Share on other sites More sharing options...
dazzi220 Posted July 12, 2007 Share Posted July 12, 2007 I'm assuming u've retuned it? if its a air leak its a big one on the engine, bearing possibly. Quote Link to comment Share on other sites More sharing options...
cew27 Posted July 12, 2007 Share Posted July 12, 2007 i have this problem with my crt ... i dont think its a huge leak with mine as its new and runs like it should Quote Link to comment Share on other sites More sharing options...
M@1 Posted July 12, 2007 Author Share Posted July 12, 2007 (edited) try filling the tank up to the brim and see if bubbles go away if so leaking fuel tank I fairly sure the fuel tank does not leak as I have put my finger over the pressure pipe inlet and blown down the fuel line (with fuel in the tank) and the fuel does not bubble whereas when I take my finger off and blown through it, it bubbles Have you checked the carb and bearings for air leaks? I have looked at the carb and couldn't see anything obviously wrong with it. How would I go about checking the bearings for leaks? Also it was bought second hand so I can't really return it (it didn't have the problem the first few times I used it). Edited July 12, 2007 by M@1 Quote Link to comment Share on other sites More sharing options...
Samari Posted July 13, 2007 Share Posted July 13, 2007 Put the engine underwater and blow into the fuel tube to see if any bubbles come out. Make sure you cover the carb and exhaust valve with your thumbs. Any leak will probably be too small for you to visually notice. Quote Link to comment Share on other sites More sharing options...
Matt B Posted July 13, 2007 Share Posted July 13, 2007 A quicker way to test is to start it up, ans spray WD40 on the carb, then the backplate, then the front bearing and listen for the revs going up. If you hear the revs going up in any of the places, then this is where the leak is coming from. Quote Link to comment Share on other sites More sharing options...
M@1 Posted July 21, 2007 Author Share Posted July 21, 2007 (edited) A quicker way to test is to start it up, ans spray WD40 on the carb, then the backplate, then the front bearing and listen for the revs going up. If you hear the revs going up in any of the places, then this is where the leak is coming from. I got a chance to try this today and I found that when I spray WD40 onto the front bearing (between the flywheel and cranckcase, not sure whether thats the front bearing or not but I assume so) the engine cuts out almost instantly. Is this supposed to happen? I'm guessing not but I don't really understand what causes it to stall. Any ideas would be greatly appreciated. Edited July 21, 2007 by M@1 Quote Link to comment Share on other sites More sharing options...
Matt B Posted July 22, 2007 Share Posted July 22, 2007 Well i'm unsure if it should raise or lower the revs, we need Ziggy in here! If it cuts out every time then i would have thought it would have a leak. Quote Link to comment Share on other sites More sharing options...
dazzi220 Posted July 22, 2007 Share Posted July 22, 2007 yes he does Quote Link to comment Share on other sites More sharing options...
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