Suzuki DT100 2 stroke

[Jonboy]

Problem-Engine starts & runs (almost) ok on tickover, try to power up & you only reach about 4000 rpm if you are lucky. Eventually the engine revs back down to almost tickover speed & cuts out with splut. (Fuel starvation, I hear you cry!)<br />Main tank has been cleaned out & refuelled, new primer bulb fitted, filters replaced after the main engine rebuild by a 'service engineer' We cleaned out the carbs & blew the jets clean, even replaced the water pump impeller to eliminate the chance of the overheat sensor coming into play. <br />Fuel pump diaphram was also replaced by engineer.<br />Reed valves knackered or the expensive power pack?<br />Hellllllllllpppppppp anyone out there???

 

[jim dozier]

Re: Suzuki DT100 2 stroke

Are you saying that you had the powerhead rebuilt by the "engineer" with new pistons and such? If so how is the compression after the rebuild. If it was rebuilt and only turns 4000 rpm take it back to the rebuilder. If the powerhead wasn't rebuilt start with the compression. You say you cleaned the carbs. Did you remove them, disassemble them, soak them, and then clean with compressed air, or just spray the outside of them? One other thing to check is the oil injection. Suzukis have a rev limiter set off when the oil flow gets too low. Perhaps your oil filter is clogged or something else is impedign your oil flow. Some Suzukis have a reset button to overide this.

 

[Yepblaze]

Re: Suzuki DT100 2 stroke

What year is that thing?<br /><br />On some older models the foam hood liner deteriorates causing bits to get into the main jets through the bowl vents. It can cause repeated need for carb jet bowl clearing till the foam liner,and errant particles are removed.

 

[fridays]

Re: Suzuki DT100 2 stroke

Go back to your fuel pump. You have the classic symtoms. Assuming diaphram is ok check the small (about the size of a nickel) clear plastic valves. I have seen them break..rare but not unheard of. If it was a reed it might not rev but it wouldn't die. Electrics are unlikely as Suzuki electrics are pretty bulletproof...BUT... do you have resistor plugs in it? If not put them in as standard plugs have stray radio waves that will definately mess with the Microlink computer ignition. If it is one of the shut down systems (oil flow, low oil, water flow) it wouldn't rev past 3000rpm but once again wouldn't die on you. Before you do any of the above put a timing light on it and see if the advance is working. It could very well be your throttle switch which is about the only weak link in the ignition. Good luck..Phil

 

[Jonboy]

Re: Suzuki DT100 2 stroke

Thanks for all that advice guys, some more info for you all. This engine is a 97/98 model with low hours. I have stripped out the carbs(I mean totally dismantled them with jets removed & blown through)& also the reed valves, they are all in good shape, as is the fuel pump & diaphram. I tested it pumping clean fuel. Brand new plugs & those expensive yellow caps were fitted during rebuild. I also blew through the oil tank filter believing that it may be clogged.<br />After running the engine in a rather large tub! I checked the spark plugs for condition & lo & behold drops of water on the top of the plugs on one side of the engine only!!!!!!!! <br />Now this combined with the water cooling jet ****tering out water & air makes me think that we have a blown head gasket!<br />I have taken it back to the 'engineer' for a compression test but as he did not remove the cylinder head/s during rebuild, ('cos the lower oil crankcase seal had blown) I doubt if I can blame him. S**t happens! Thanks again, what a good site & the sun is shining in England for a change!

 

[jim dozier]

Re: Suzuki DT100 2 stroke

So you didn't actually have the power head rebuilt in the traditional sense. You had the lower crankshaft seal replaced. It sounds as if the mechanic did not have to crack the case even. Odd that an engine with low hours would need a crankshaft seal but whatever.<br />1. Get the results of the compression test.<br />2. The fact that you see evidence of water on one bank of cylinders suggests a head gasket leak. If the head bolts come out without difficulty it is a simple task to remove the head, examine the gasket and mating surfaces and inspect the cylinder walls and the tops of the pistons. Perhaps all thats needed is to replace the head gasket and be on your way.<br /><br />By the way what were the symptoms that led to the replacement of the crankshaft seal? 90 degrees F. and sunny here.

 

[Jonboy]

Re: Suzuki DT100 2 stroke

Hi again, the symptons before all this happened were very similar. i.e. loss of power, unable to reach any planing revs, engine kept stalling.<br />The engineer said that there was oil splattered all inside the compartment causing loss of power.<br />The boat, by the way is a 21ft RIB that we using for diving out in the English channel mostly. The good old German Subs made some great dive sites for us! Still sunny & 55 degrees

 

[jim dozier]

Re: Suzuki DT100 2 stroke

I think that it is really cool that you have engineers work on your outboards in GB. Over here we just have mechanics. I think you should pull the head (wet plug side).

 

[Jonboy]

Re: Suzuki DT100 2 stroke

When I get the results of the compression test I expect they'll want to take the head off for inspection (more money!!) I'll let you know how it goes. (Actually I was being kind, we usually call them grease monkeys)!! Thanks for all your help, I'll keep checking this site & help out if I can.

 

[Jonboy]

Re: Suzuki DT100 2 stroke

The latest news is that the engine has blown a head gasket. Some guy had stripped one of the threads on a previous removal of the head & under pressure it had allowed the gasket to blow. Hence air mixing in with the water cooling giving the spurting water & air mixture. On powering up the engine, loss of power & cutting out. Well, you live & learn don't you? The engineers,(mechanical grease monkey's,) are going to skim the head & repair any damage done at not a bad price & hopefully we can get back on the water soon, we have a very short diving season over here! Thanks for the advice fella's.