Did we siez up the Losi 5T

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
B

Braapdaddy

Member
Messages
24
Hello forgive if this is a old subject

My boy was running the 5T 2.0 today and nothing at all seemed out of the ordinary untill it all of a sudden bogged out and died

Upon inspection it seemed to be binding thru the clutch and or crank shaft when attempt to move it fowards or backwards by hand far more resistance than ever before it also pulls from the cord way harder than normal

Removed the typical things for inspection the clutch was not binding at all and with the engine out the drivetrain is 100% like it should be

Removed the plug and pull to see how free the engine pulls and it dose not seem to have any binding resistance until i put the plug back im and the compression is far to much resistance aganst the pull cord

Removed the cylinder to see the mains and the bottom bearing on the rod no scores no purple no visually bad bearings ........

Its nice and oily down in the bottom end like it should be

I am not an expert on these cars but we do race motocross and i do know enough to do those engines and no issues for rebuilding the top end

But i see no visual reason and no smoking gun for why its all binding up

Aprox 6 hours running Klotz supertechniplate
And 2 hours running Lucas full syn 2 stroke


My only weak link i can pick is the last batch of gas was weak and old

Thanks i can will try to get pics of the internals to see if anyone can get any visuals on my wear and condition
 
None of the above clutch is off engine is out in hand

With the head off the crank and everything spins freely no binding no scoreing on cylinder wall

I guess its possible the wrist pin tolerance is out of spec and or the same on the bottom at the crank and its geting to much side to side movement and binding some

Pics to come soon
20211024_174750.jpg
20211024_174841.jpg
20211024_174800.jpg
 
deathrawt said:
Did you try spinning the engine over after you had the clutch and coil assembly off but before you removed the cylinder?
Click to expand...
Yes sir i did ..... i have had lots of honda and suzuki two strokes apart i cant see any issue

I guess my next step is to get some gaskets and go back together one time and bolt it back down minus the clutch assy and see if i can get it to fire back off

My only fear is the factory air filter let too much pass by and it just wore sometning out like a main bearing or ????

Should i split the case and look before reinstal

How many hours of " normal" run time on a top end or whole engine for that matter ????

Any red flags in my cylinder pic??
 
From your pic it looked like your cylinder looked a little rough so I opened up a new top end kit I have for a zen 32 and it looked identical so that's not the issue
Yep I would split the cases and check the bearings and crank you might as well as your gonna need a gasket kit anyway. Maybe some crud got in there and damaged a bearing.
As far as longevity on these engines I think it boils down to having correct oil/fuel mixture, good air filter and driving habits (not keeping the engine pinned for long periods or over reving the engine while airborne off jumps)
I have a Trevor simpson reed engine in my Baja and I let my bosses kid drive it once and he never had the throttle off of full, I thought that engine was gonna blow apart but it held together.
I think it did lose some life expectancy though! lol
 
deathrawt said:
From your pic it looked like your cylinder looked a little rough so I opened up a new top end kit I have for a zen 32 and it looked identical so that's not the issue
Yep I would split the cases and check the bearings and crank you might as well as your gonna need a gasket kit anyway. Maybe some crud got in there and damaged a bearing.
As far as longevity on these engines I think it boils down to having correct oil/fuel mixture, good air filter and driving habits (not keeping the engine pinned for long periods or over reving the engine while airborne off jumps)
I have a Trevor simpson reed engine in my Baja and I let my bosses kid drive it once and he never had the throttle off of full, I thought that engine was gonna blow apart but it held together.
I think it did lose some life expectancy though! lol
Click to expand...
Yes i am afraid the factory air filter may have been its downfall but im getting a gasket kit and will split the case and go back togetger
 
Usually the rule of thumb is check the things that are easiest to fix first. When the motor “seizes” like that it usually in the clutch area or the coil dropped. Because you disassembled the engine and everything seems to be fine i think it’s one of those two issues. I’d just put it back together and see if it’s happy
 
just re read everything you said mate,
obviously nothing binding now its apart by what you say, but whenyou said resistance when car pushed forwards and backwards through clutch and cank,
sounds like the clutch was possibly stuck engaged at some point,
is there any purple/blue colouring on the clutch shoes themselves, and on the bell?
the only way for any drag to happen at the crank is if the clutch is dragging,
may have over heated the clutch and transfered heat and a possible mild heat nip/seize at the cylinder which freed off as it cooled down,,
also fried clutch bell bearing could cause drag when free wheeling the car back and forth,
just trying to give you a cause and a couple of other checks (y),

if you do split the cases have a good look at the key way on the flywheel to see if the flywheel did come loose and spin a bit/damage the key way or key,
 
RcJunkie13 said:
but why is the prob only there when the plug is in?????? Just try a new plug I know it don't make sense but still
Click to expand...
yeh but that was just after it happened junkie, could just have dumped fuel in the case when it bogged and died then its hard to pull over cos it was flooded,
may have even been coil/plug failure that caused the bog as well,
but going off what op said its sommat clutch/bell related as well,
could just be a few different things happening all at once (y)
 
It didn't seize if you could pull it over. Seize means it stopped dead in its tracks, and normally transfer and scoring is present. That top end looks fine. The bearings will let you know right quick if they are shot. Your a motor cross guy. Same animal just smaller. I agree with spents, I think you over looked a small detail somewhere. If the air filter let crap in you would know it pretty quickly as well. Loss of compression would be evident, as well visible dirt Ingestion throughout the carb, Intake, bottom end, intake side of piston and cylinder walls. This could be as simple as the metering diaphragm got a hole in it and it flooded the engine out, as well as what was previously mentioned.
 
Yes guys i put it all back together and evrything fired right back up ...... it certinaly had to be the clutch bolts were backed out

I was having my 13 year old do the teardown as i was coaching him step by step on the parts and thier meaning

I have did not spit the case becuase everything seemeed clean and tight we did thread lock a few things and antisiezed a few things and its back to 100%

Now its time for a pipe and a far better air cleaner some of the neat ones with the air breather are sold out

Thank you everyone for the quick responses and the helpful tips
 
Back
Top
✖
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks