Hi everyone!...

I am new to this site and I need HELP!!....LOL!!

(BTW...I posted this in 2 different threads to get as much exposure as possible so I can resolve this issue quickly...my apologies if the double post irritates anyone)

Sorry if this gets windy but I want to be as detailed as possible...

So here goes...

I own a bike shop and usually (read:ALWAYS) work on 4-strokes but one of my customers owns a 2004 Suzuki lta-50 and was complaining about it bogging down at higher r's and wondered if I could fix it for him..so of course being the adventurous type of person that I am I decided to take it on and see if I could get the bike running right for him...I figured..."heck..it's just a 2-stroke so it can't be THAT difficult to trouble shoot and repair"....HAHAHA..was I wrong!!

The plug looked pretty good (better than I expected actually) so I ruled that out as the main problem right away and moved on to carburation (which is usually the root of a LOT of evils with 4-strokers)..I tore it down and cleaned everything good and the jets were all clear...etc...so I tried running it again with the same results...and by the way I also drained the tank...cleaned it out and started with fresh gas so we can rule THAT out as a possible issue...

When I tore the carb down I noticed quite a bit of wear on the slide so I suggested to my customer that we try a NEW carb and he agreed seeings how they aren't that expensive....while I was waiting for the carb to arrive I decided to pop the head and jug off to see how things were doing since the bike is 4 years old and has a LOT of hours on it...well needless to say the piston was showing some pretty good blow-by and there was some slight scoring on both the piston and cylinder walls so I was like "O.K..losing compression and we caught it in time" so he had me go ahead and get a piston and ring set for it also...

Well...I got all the parts the other day...I cleaned all the cylinder ports out...honed the cylinder and put the thing all back together yesterday afternoon and was POSITIVE our problems would be solved and it was going to run like new....well once again I was WRONG!!...she starts right up and idles great but STILL has the upper "R" bogging thing going on...while I was trying different things I discovered what I THOUGHT and what SHOULD be the float bowl drain tube is not actually the drain tube at all...it has VACUUM!!..whats up with that?...just to be sure I sprayed a bit of carb cleaner into that line and killed the engine of course....now..I'm not stupid but this bike has been apart for some time and I can't see ANY place this line should go to...I am completely STUMPED at this point and needless to say with all this time spent trying to trouble shoot after rebuilding the top end I have lost my butt on this job...LOL!!

This all just does not make ANY sense!...can anyone possibly shed some light on this for me??...like...what the heck is that vacuum line doing at the bottom of the float bowl...where does it go (I honestly don't remember it hooked up to ANYTHING when I tore it down) and why is this thing still bogging when you try to give it some rev's?

Any and all advice you may be able to give me would be GREATLY appreciated as this has drug on WAY too long and I need to get it out of my shop....HE is O.K. with things but his wife is starting to get pissy (go figure..LOL!!)...

Thank you in advance and I hope to see some useful feedback soon!

 

One thought. Two stroke are famous for plugging up the exhaust when cheap two cycle oil is used like generic Valvoline. Ask the customer what oil they are using and it might help. Also be sure to remove the pipe plug at the bottom of the muffler, cover up the end of it and let the muffler blow out of the plug hole to clean it out. I think the owners manual explains this. I no longer have our '03 so I can't check for you.

If you do a search, you can also find other quick performance mods.

One more thought - be sure the restricter cover is off the carb intake to utilize the most air into the engine.

 

<div class="FTQUOTE"><begin quote>Originally posted by: inthedirt

One thought. Two stroke are famous for plugging up the exhaust when cheap two cycle oil is used like generic Valvoline. Ask the customer what oil they are using and it might help. Also be sure to remove the pipe plug at the bottom of the muffler, cover up the end of it and let the muffler blow out of the plug hole to clean it out. I think the owners manual explains this. I no longer have our '03 so I can't check for you.



If you do a search, you can also find other quick performance mods.



One more thought - be sure the restricter cover is off the carb intake to utilize the most air into the engine.</end quote></div>


Opened the plug and checked the exhaust and it's all clear...

I am wondering if removing that restrictor will make it necessary to re-jet??..it seems to me that would lean it out quite a bit wouldn't it?

I noticed one thing that strikes me as kind of odd....if I stick my finger in the carb opening and restrict the flow very slightly and I mean BARELY the thing will run a lot better...so that would lead you to believe it is running too lean already...correct?...but when I checked the plug it shows rich....UGH!!!

I am still baffled by the open vacuum line coming out of the bottom of the carb...surely that would have to conect to SOMETHING shouldn't it??...if not why would they have a wide open vacuum sucking dirty air directly into the air/fuel stream??

ANY and all advice is greatly appreciated!!

Thanks for the response!!

 

Our set-up was pure stock other than mounting the wheels inside out to widen it a bit. When we removed the restricter, it did not affect the mixture. Do not rejet for this reason alone. I'm not as familiar with a two stroke carb as a four stroke but in that world, the bogging at higher rpms would point to a partially clogged main jet. It's possible fuel was sitting in this carb and gummed it up. Sometimes it as simple as unclogging a float bowl vent not even jet related. I would take the carb off, remove every jet and run through every orafice with a piece of bailing wire and a pin if need be. I think you have something clogged and my bet is on a vent. I can tell you that I went through a Yamaha 350 carb several times before I found the vent problem and then it ran perfectly.

For the vacuum question, I would try to find a schematic for the carb on the web. Try searching "suzuki lta-50 manual". I don't know the answer to that one but I will look around for you. Are you sure that it is not an overflow tube? Maybe it is venting through this hose because of the normal vent being clogged. Stranger things have happened.............

Is the replacement top end the same compression ratio? Is it oEM?

 

Here's one more thing you should do that I found (and remembered afterwards):


Take off the intake manifold from the carb and head. You will see a slotted restrictor in the side nearest the head. Heat up the aluminum intake with a propane or map gas torch and the restrictor will fall out.

I believe that I did not have to heat it to get it out.

 

Check to see if the restrictors had been removed yet. Simply removing them will make a big difference in the way it runs.
-The exhaust restrictor is a washer in the pipe at the head.
-The intake restrictor is in the intake elbow.(heat to melt the adhesive & pry out w/screwdriver)
The stock main jet is a 56, that will run fine with just the restrictors removed. If the stock air/filter had been modified to allow more air flow, then you might want to jump up a few jet sizes.
-There are two pilot jets that are piggy-backed on top of each other. Some people prefer to remove the first one, but I found that my son's machine seems to run the same either way.
-I run a K&N filter with a 65 Main jet with the needle clip in the top position with good results.
-you can find an exploded view of the carb at bikebandit.com
-good luck, hope this helps