Martin Harris - Moderator Posted September 21, 2009 Share Posted September 21, 2009 If the piston is in the bore it is very obvious i.e. it's when the piston is at the top of its stroke. Otherwise, ensure the crankpin on the end of the crankshaft is sitting exactly in the middle of the crankcase and at the top. Some engines with keyed on prop drivers (not Saito) will have marks on the driver for TDC alignment but you can feel for TDC with a soft probe (matchstick or similar) through the glow plug hole if the engine is still assembled. Quote Link to comment Share on other sites More sharing options...
Klippy Posted September 25, 2009 Share Posted September 25, 2009 Any joy on this motor Andy? Quote Link to comment Share on other sites More sharing options...
andy watson Posted September 25, 2009 Author Share Posted September 25, 2009 Well I rather scarily took it apart last night. Martins link above was very helpful and unhelpful at the same time. I used it in conjunction with an exploded view of the engine. The reason Martins link was unhelpful was I couldn't seem to insert the 2mm allan key I was using into any hole on the camshaft, but maybe I didn't have it centred properly. The second diagram did show me clearly what I needed to do with the toothed wheel. I then used the afore mentioned allen key. I took out a glow plug and poked the allen key in to measuse where TDC was on the piston. Then I stuck the 2 bits together. A conference at work has stopped me testing it out until Sunday. More to follow. BTW I asked Just Engines for a quote on fixing the timing and a service (I rang them because they donated a prize at our recent fun fly day). £35ish which was reasonable except they don't have saito parts and I would have needed to source any needed myself. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 25, 2009 Share Posted September 25, 2009 Possibly due to a 2mm allen key being 2mm across flats so its "diameter" would be a little more than 2mm... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 25, 2009 Share Posted September 25, 2009 For info, I got my log tables out (well, M$ calculator) and a 2mm allen key would be the equivalent of a round bar fractionally larger than 2.3mm diameter so there's no chance of it going into a 2mm hole...next time try using the shaft of a 2mm drill - although, of course, if both the hole and shaft are accurately sized it still wouldn't slide in - you would need a small amount of clearance. Quote Link to comment Share on other sites More sharing options...
andy watson Posted September 26, 2009 Author Share Posted September 26, 2009 Well a partial success........... The engine seems to be no longer blowing fuel away, but still not effort on firing. Also there seems to be very little compression now. My only thought was when I measured where TDC was, I used the prop as an indicator- straight up = TDC. I suppose it's possible the prop got turned 180 degrees when I was putting the engine back together. I will disassemble it tonight and try again tomorrow, otherwise it gets sent away! I would like to get it fixed myself if possible though. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted September 26, 2009 Share Posted September 26, 2009 That would be a very rwarding moment if you could Andy.I had a bit of a deal with an OS90 4 str.When we tried to start it it also had no compression.I stated by checking the tappet clearance,it was 10 thou,I reduced it to 5thou and it started.I ran it for 10 min and the compression was then there.Il reduce the clearance to 5,wrong to 4 thou when I fly itI hope it works out for you.In 1 of the vintage models a Murco 61 was seized abnd when i managed to free it and get it running it was a great feeling Quote Link to comment Share on other sites More sharing options...
Aslan Posted October 2, 2009 Share Posted October 2, 2009 Hello all.Havn't read through the whole of this thread so forgive me if I repeat someone elses thoughts.Not sure of why the engine was dismantled,but TDC is on the compression stroke,so be careful there.Using the prop to find TDC is a no no.As Martin said it definitely wasn't timed as a pusher.....a pusher prop is used.You might have paid too much attention to the fact that fuel is pushed back on the feed to the carb.this is normal as is a certain amount being spit out of the carb at times.Before you dismantled the engine did you check that the valves were opening and closing properly,easy to check by removing the plug. Only run the engine with the muffler attached and a pressure feed to the tank.I have several saitos and the system I use to start them is finger over the exhaust and turn three times by hand anti clockwise,you should feel the pressure on the tip of your finger as it sucks fuel in.Then remove finger and flip 3 or 4 times clockwise to get fuel into chamber.Apply glow start and starter. Works 99% of the time for me. Quote Link to comment Share on other sites More sharing options...
andy watson Posted October 9, 2009 Author Share Posted October 9, 2009 Well, it's going. I haven't actually seen it running, but it is! There is someone in the club that builds his own engines. I hadn't seen him for a while, but at the last club meet I remembered to stick the engine in the car and luckily he was there and agreed to have a look. He took it to pieces and reset the timing and with a bit of fiddling has it going! He is very impressed with it- says it's giving out loads of power and doesn't show much sign of wear, so good news all round! Quote Link to comment Share on other sites More sharing options...
Aslan Posted October 10, 2009 Share Posted October 10, 2009 Did he say what was wrong with it Andy? Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted October 10, 2009 Share Posted October 10, 2009 good news Andy Quote Link to comment Share on other sites More sharing options...
andy watson Posted October 10, 2009 Author Share Posted October 10, 2009 The timing was wrong, but I had fiddled with it, so it's possible I messed that up. He did say there were other bits and pieces that weren't right, but to be honest it was all above me- I didn't know what half the bits were he was referring to! Anyway, I was delighted to get it sorted, and he seemed delighted with the half gallon container of fuel I gave him as a thankyou. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted October 10, 2009 Share Posted October 10, 2009 What have you learned from it Andy,a meticulous engine guru checked a newish Thunder Tiger 46 Pro for me as it kept dead sticking.He found some debris in the carb.I flew it on Wed.2 perfect flightd,3rd deadstick on take off,landed the model well and broke the fuz,what have I learned,I dont know,I need help. Quote Link to comment Share on other sites More sharing options...
Aslan Posted October 18, 2009 Share Posted October 18, 2009 How about,one should never dismantle an engine unless one knows what one is doing......especially a four stroker. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 18, 2009 Share Posted October 18, 2009 Posted by Aslan on 02/10/2009 13:23:53:Not sure of why the engine was dismantled,but TDC is on the compression stroke,so be careful there.Using the prop to find TDC is a no no. No need to get too hung up on this - although the engine will only fire at (technically a little before) TDC on the compression stroke, for the purposes of timing, TDC is TDC. As the camshaft rotates at 1/2 crankshaft speed the engine decides which is the compression or the exhaust stroke.Edited By Martin Harris on 18/10/2009 20:52:47 Quote Link to comment Share on other sites More sharing options...
andy watson Posted October 19, 2009 Author Share Posted October 19, 2009 I have to be honest and say the thread is now moving beyond me! Why was the engine dismantled- because it wasn't working. I was given some excellent advice on here as to how I might be able to get it running properly, which looks as if it was pointing to at least part of the problem. I think there might have been other issues as well that I wasn't aware of or that didn't have the experience to recognise. Having said that taking the engine apart was not difficult, and neither was putting it back together. So rather than immediately spending £50 to send it off to have someone else fix it then it is worth having a go myself. Afterall what would I learn by sending it off? Would I dismantle a working engine- well no, but one that isn't running is worth a bash. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted October 19, 2009 Share Posted October 19, 2009 As you say Andy Its the only way you will improve your mechanical knowledge about your engines by investigating.Ive just stripped an old OS40 4 stroke because its become very noisy.I believe its the bearings.,that holds the crankshaft.The only problem Ive come across is how to get the conrod off the crank.The camshaft fell out and Ill need to figure out how to time that when its time to put it back together Quote Link to comment Share on other sites More sharing options...
Aslan Posted October 19, 2009 Share Posted October 19, 2009 No Martin, we won't get hung up at all,didn't think I was,and you are on the button regarding TDC (it can also be advanced slightly,as you know).But as Andy did not know,there was a chance that he might have gone on and adjusted the tappet clearance, assuming TDC was prop pointing up,so I thought it important for him to know that there was a difference,so generally,imho,we assume TDC to be on the compression stroke. Really not sure what your point is to be honest.Andy,I was just wondering why you dismantled the engine,no malice or intent at all.And in your own words,no disrepect,you have no experience with the interior workings of an engine,let alone a Saito.After you tried all the other things which can go funny,you did the proper thing, and handed it over to a fellow member,and got a result. I found, that someone mentioned timing and all hell broke loose.then TDC came along and the plot thickened.........love itAlso Saitos are my bag,got loads of 'em across the range.....and the last thing I do is dismantle them,but I've done it many, many times.Edited By Aslan on 19/10/2009 11:58:27 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 19, 2009 Share Posted October 19, 2009 Just trying to clarify the point for the benefit of anyone less familiar with engines than yourself, Aslan. I have to say that I would invariably quote "TDC on the compression stroke" if I was advising someone about where to set the valve clearances. Hopefully these postings will help Andy's understanding a bit. Lovely engines, Saitos and they do deserve TLC... Quote Link to comment Share on other sites More sharing options...
Aslan Posted October 19, 2009 Share Posted October 19, 2009 ooooooooh Martin,Martin Martin....getting a hint of sarcasm here, just for posting an alternative view on one issue......and yet agreeing with you on others?????tut... tut... tut.....No need to be like this to people who offer other options,especially from the likes of meself,Aslan, who knows absolutely everything about Saitos......Come on man,chill,I'll get me coat and say goodbye.Andy,If you get into taking engines apart,and you should do 'cos it's really interesting,pick up a copy of Harry Higleys book on the subject,it is a fantastic and very informative read.Now down to me shed,lathe work tonight,to work on a home built Radial I'm working on with two fellow engineering pals.....oops,am I leaving meself open to more sarcasm here......Oh, who cares.....Goodbye cruel world Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 19, 2009 Share Posted October 19, 2009 Don't know where it's coming from - none was intended! I just thought your post, essentially correct as it was, might be a bit confusing to a beginner.and posted to clarify it. If you read anything more into it then I apologise for not making myself clear! Quote Link to comment Share on other sites More sharing options...
Aslan Posted October 19, 2009 Share Posted October 19, 2009 Apologies....took the first sentence up wrong.Thats the damn thing about the written word Martin.....Same thing with the bible,one book.....many religions....and worst of all, too many wars. Quote Link to comment Share on other sites More sharing options...
andy watson Posted October 20, 2009 Author Share Posted October 20, 2009 Well I have had it running in the garage- sounds fantastic, looks like lot of power, nice stable idle. But.......... although it was very easy to start, it wasn't for the first time. In the end I had to drip a bit of fuel into the cylinder through the glow plug hole (once it was taken out). Then it started immediately. What causes this need to "wet" the plug and how do I avoid having to do it every time I start from cold? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 20, 2009 Share Posted October 20, 2009 Follow Aslan's advice in his first post (Page 2) and you should be OK. Saitos do like to be nice and wet to start. Could also relate to tank height being too low on your test rig.Edited By Martin Harris on 20/10/2009 21:02:15 Quote Link to comment Share on other sites More sharing options...
Aslan Posted October 25, 2009 Share Posted October 25, 2009 Andy,I strongly recommend that you do not remove the plug and drip fuel into the cylinder. There is a chance that you could hydro lock it i.e. to much fluid in the cylinder, making it impossible to turn over,and you will have to go through the whole process to drain it out. I think you should read up a bit more about your Saito,and keep your fingers well away from it. Make sure you use a chicken stick when flipping it back,with no glow start on. Sorry if I'm stating the obvious here, but I'm getting the impression that you have very little experience here(no disrespect Andy)and would advise that you seek some practical advice from fellow club members. These engines can.... and will bite hard.We all know how frustrating it can be, trying to start a stubborn engine, which can lead to a momentary lapse in concentration.... and that's when a large razor blade, spinning so fast you can't see it, can do math subtraction on the pinkys......... not nice. Quote Link to comment Share on other sites More sharing options...
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