Gs250t Vacuum Leak Bike wont catch

[jake]

Hi Gorminrider,

Thank you for your input, reading over what you said, I will double check again all the jets. I would be very alarmed if my mechanic had anything against me, I'm a new motorcyclist, they're family run, and they put on the new tyres where no one else would touch a bike this old (im in Ireland), also bought all my gear from them.

I am relatively familiar with compression, spark etc... I wouldn't have posted in the forum if I wasn't. Unfortunately I am not in a position to buy new tools let alone pay for transport etc... I bought the bike because it was relatively cheap, and I was told by a couple home mechanic relatives (who have all had a look) that older bikes very rarely broke down.

I thought that the leak may have been responsible as the symptoms preceding the bike breaking down seemed very similar to what I'd read online about vacuum leaks.

Thanks for explaining the operation of the vacuum operated carbs, I had had them mostly apart, however I did not want to take them apart fully for fear of being unable to rebuild them in case the rubber elements were too degraded.

I will recheck, fuel, valves, petcock, and jets

thankyou

[Nessism]

It goes without saying that you should fix all the vacuum leak passages. The bike won't run right with gaps on the intake passages like you mention. It should run though.

[Gorminrider]

Unless someone has modified their bike, that is not possible with a GS.

Turning the kill switch to the OFF position also disables the starter.

Now, ... if the bike has a kick starter, you can kick it a bit, but you don't even have to have the key ON, so it won't matter what position the kill switch is in.

.

right. Sloppy- but mainly, squirting a little gas in through the airbox before turning it over should give a useful reaction...even if the airbox screen is in the way .

[Gorminrider]

Thanks for explaining the operation of the vacuum operated carbs, I had had them mostly apart, however I did not want to take them apart fully for fear of being unable to rebuild them in case the rubber elements were too degraded.

Dirty idle jets are very common. Cleaning the bowl and pulling out the jets to clean does not need the vacuum slides disassembled.Otherwise there's few to none rubber o-rings involved until you pull the float needle seat or the idlemixture screws or the bowl drain screw. and usually these are ok anyways- certainly good enough to start the bike while dirty jets are NOT.
Being careful not to tear the bowl gasket is the main hurdle.

https://www.cmsnl.com/suzuki-gs250t-1980-t-united-kingdom-e02_model13417/partslist/FIG-12.html

[jake]

Hi All,

I know it has been some time since I last was in touch with you all. Although I have still not had the time or other resources to recheck the various items that were mentioned e.g. valve clearances, I was offered a free tow and check by a vintage mechanic... The mechanic cleaned the carbs and returned them to the bike, and the bike started up, he said no bother. I rode the bike back home all in good condition, however within the space of about 3 days the engine died again, I had used it every day since getting it back and didnt have an issue... I haven't been in touch with the mechanic yet as I am in the midst of very tough exams, I hope to be able to get around to him some time in February... In the mean time however I wanted to ask what you guys thought might be wrong with the bike... the mechanic said the bike would continue to run for decades to come and that there were no other problems with the bike... I am truly stumped... If anyone has any further light to shed on why this problem might be recurrent or even what it is would be very much appreciated... I have only been able to ride the bike for 3 months and paid out 1800 for insurance and 1000 for the bike which I was hoping to be able to rely on for more work... I lost my job because it broke down... I dont want to have to end up selling the bike for scrap and losing my license which I paid another 600 for...

Many Thanks,

jake.

[fbody_mike]

From your last post, I'd assume the tank has a lot of rust or dirt. The mechanic cleaned the carbs and fixed the no run condition but not the cause. Drain all the fuel from the tank into a bucket and see what is in it. if there is particles then you will need to get the tank treated and lined.

[tom203]

From your last post, I'd assume the tank has a lot of rust or dirt. The mechanic cleaned the carbs and fixed the no run condition but not the cause. Drain all the fuel from the tank into a bucket and see what is in it. if there is particles then you will need to get the tank treated and lined.

I agree ....debris from tank gunking up petcock and carbs. Drain tank and look inside with flashlight

[jake]

Hi fbody,

The Tank has a very small amount of rust, but I'm not sure dirt's the issue, I had the carbs apart and cleaned them myself twice before sending it in and didn't have any luck, and he said all he used was carb cleaner spray... The bike won't even cough on starter fluid... Good spark and good compression... He mentioned something about a potential blocked overflow passage, but when I asked he said he didn't know enough about the carbs on it, he didn't even have them apart... Rust is definitely something to consider, but the fuel was extremely clean, I've drained in small quantities (and let sit) about 3 cups, no water or dirt... I am puzzled...

[jake]

I will have another look and will drain the tank and reclean the carbs again... However it might take some time given my workload and the lack of daylight, thank you for your advice.

[jake]

Hi all,

Thank you for your patience for me to get back to you. I have some good news, I drained the tank entirely and found there to be no rust or water. Then I recleaned and rechecked the jets and carburettor, and put everything back together. Put in a freshly charged battery, refilled with fuel, primed, choke on, and pressed the starter... and lo and behold, the bike started up... fantastic. I let it warm up and took it for an hour spin or so, as all sounded very well. A couple of problems developed throughout the ride however. The ignition system at one point went dead, the headlight high beam/low beam indicator began flickering, then the engine died. The starter motor wouldnt work either, I noted water from the kill switch and put it down to a short. After a little drying the starter worked and all was well. The second issue was power, I didnt have has much power in the bike as I had beforehand, and the sound of the bike could be described as flat, and produced a sound almost like very quiet backfiring. I am not sure what could have caused this. The bike would not start unless on the prime position of the petcock, could this be due to a lack of the required pressure, or petcock failure? The last problem I have is that the battery is discharging throughout the evening, I am not too bothered by this right now, as I just want the bike to run properly so I have put on a switch to cut off the battery completely.

The bike was still hard to start however and I noted that the airbox was not able to fit fully/properly to the carburettors and were placed at an angle, I was going to test for vacuum leaks today, but the battery discharged and is also low on fluids, I couldn't get the bike started. I will be topping it up and recharging tomorrow. Does anyone have any suggestions for more tightly fitting the airbox? The exhaust manifold is scorched (when I got the bike) which makes me think lean mixture alongside poorer power output, but the spark plugs that came on it seemed fine. The battery dropped fluids quite fast from when I last checked it, I am told that it could be due to overcharging, I will check the voltage when I get it started tomorrow, could someone recommend a cheap, durable voltage rectifier if this is the case? If you don't think that may be the cause I would appreciate your thoughts.

I know I may need to order new boots and I found a set on partzilla, however if these boots are wrong, or there is somewhere else I can find them cheaper please let me know, I will have to pay shipping to Ireland regardless. https://www.partzilla.com/catalog/su.../cylinder-head

I am uncertain how to ensure the airbox is connected properly to the carbs, they dont seem to reach their mark, even with an excessive use of force and with the mounting screws. I would feel more comfortable If I could get that more properly sealed, however I am not sure how to go about this. I have had some suggest plumbers self adhering tape, however I think vulking tape may be stronger. Getting it around the carbs etc... will be a pain in the ass, any suggestions? I'm getting a little tired of having this apart (5 times!).



Thank you for all your help so far, It is indeed much appreciated.

Jake.

[Nessism]

Sounds like the charging system isn't working. There are literally thousands of posts here on how to check the system and fix it so please do some research and tests.

It also sounds like you have air leakage issues; the airbox must be 100% sealed to the carbs or the mixture will be off and the bike won't run right. Please don't monkey around with tape or the like in an attempt to seal this system. Get the proper parts. New boots that attach to the head and new boots for the airbox too that attach to the back side of the carbs is money well spent.

I'd buy those and install them, and go through the carbs properly, updating the O-rings to assure good sealing. You can do the job right one time or shortcut and have to redo it all again later.

[jake]

Hi Nessism

Thanks for your insight, I recharged the battery and discharged about 3-4 times and on the 4th go the engine started up again. I tested for vacuum leaks using carb spray and also using starter fluid and saw no change in the rpm of the engine, I presume there is no airleak. I tested the battery at idling speeds and saw that the voltage was 15.4 at 1100 rpm... which seems very high, especially for idling. I think the voltage rectifier is gone. Original rectifiers are seemingly very expensive, I am hoping to wire up a more universal connector to use with newer rectifiers. I will do further research, but if anyone has a diagram or a quick summary of the wiring as a guide, it would be much appreciated.

Many Thanks.

Jake.

[jake]

Also, sorry to bother you Nessism, I was uncertain about the seal between the airbox and the carbs, the boots were in a good position. I do not know where I can pick up a "new" airbox to fit more snugly, If I could be put in the right direction that would be great.

Thanks,

Jake.

[Bortasqu]

The culprit is either bad fuel or ignition problems, judging by what you have written so far.
Water in the kill switch is pretty bad, and will make your bike a no start even with starting fluid. It sounds like you got a lemon.

[fbody_mike]

https://www.thegsresources.com/_forum/showthread.php?257440-GS250T-SH775-conversion

Check out the link above. I recently upgraded the regulator on my gs250t. Sounds like you need to do the same.