eyetech Report post Posted March 17, 2016 Hi guys i'm from Portugal and i recently got a JT 25 that wasnt loved enough before and that i've been restoring it. I had to bleed all the hidraulics, changed all the bearings from top to bottom, new brake pads, new brake and clutch lever, new radiator cap and fluid, new bolts all around, fixed some exaust leaks on the joints, new chain tensioner, did some paint and a few other stuff. I'm still waiting for the air filter but i decided to test the bike anyways without him to check the engine and the clutch. Happens that i encounter some issues that i need some help specially from you guys that have more experience in these types of motorcycles. The engine starts pretty good, even on cold, but after running it for about 5 minutes i start to feel the engine loosing response (like when you're running out of gas or loosing spark) and it stalls, it doesnt start after that and i find that the plug is wet. I clean it and everything is fine for more 5 minutes or so (one time it didnt start after the cleaning). I didnt change the plug when i got this bike because the owner said it was new, and it looks like it, but i found that this plug is very small. My questions are, what type of spark plug these engines use? can this problem being caused by a not recommended plug? the fact that i'm not using air filter? could this be to a bad adjustment on the carburetor or some other problem related to energy? The other issue i found is, when in cold, clutch in, and when i go into any gear the bike jumps and wants to go and i have to brake to stop it, once i leave the clutch it goes fine (you cant feel this force so much when is warmer). Related to clutch and gears, some kind of sorcery is happening that the bike goes into gear by itself, happens only from neutral to 1st or 2nd, with engine on or off. Today it happened at the same time i was kicking in neutral, suddently went on gear, the engine started and i had to run to catch the bike lol.If someone can give me some tips i would really appreciate, thank you in advance!!! Cheers Before and after pics: Quote Share this post Link to post Share on other sites
dadof2 Report post Posted March 18, 2016 Pretty certain plug is an NGK BP5ES Get an air filter before trying anything else. Often cutting out after a few minutes running and plug has fuel on it is due to coil failure. Usually HT coil but occasionally source coil. Change plug for a known good one. Quote Share this post Link to post Share on other sites
eyetech Report post Posted March 18, 2016 Pretty certain plug is an NGK BP5ES Get an air filter before trying anything else. Often cutting out after a few minutes running and plug has fuel on it is due to coil failure. Usually HT coil but occasionally source coil. Change plug for a known good one. Thanks for answering, do you have any idea if it's small tread size? because this plug from denso that i have is very small, i'm affraid to put one with longer tread and damage something. Quote Share this post Link to post Share on other sites
lineaway Report post Posted March 18, 2016 It is a BP5es. NGK not denso. Float level and the needle and seat would be cause for the flooding issues. Quote Share this post Link to post Share on other sites
crazybond700 Report post Posted March 18, 2016 Those bikes can be set quite easiliy in the wrong neutral. So between 2 and 3. Than it will get into gear by itself. If the bike is off, put in first gear, move it back an forward a bit and then put in neutral. Never ride without an airfilter!!! Quote Share this post Link to post Share on other sites
eyetech Report post Posted March 18, 2016 Those bikes can be set quite easiliy in the wrong neutral. So between 2 and 3. Than it will get into gear by itself. If the bike is off, put in first gear, move it back an forward a bit and then put in neutral. Never ride without an airfilter!!! I'm pretty sure it was between 1 and 2 and it happened a few times. I did ride without air filter but i had a sponge so it doesnt catch debree and i guess that's not what's making these issues. Quote Share this post Link to post Share on other sites
mazz46 Report post Posted March 18, 2016 Sponge used as filter? Quote Share this post Link to post Share on other sites
cbutler Report post Posted March 18, 2016 You need to get a skid plate on there too it is the bottom part of the frame Quote Share this post Link to post Share on other sites
dadof2 Report post Posted March 18, 2016 Check the reach (length of threaded part) of the that the plug should be by measuring the thickness of the cylinder head with a bit of hooked wire in the plug hole. It will be about 19 to 20mm. If you are using a short reach plug it could be causing the problems you are having Quote Share this post Link to post Share on other sites
eyetech Report post Posted March 18, 2016 Sponge used as filter? to test some things i've done on the bike, imagine buying a used bike and spending 3 weeks restoring it, you wouldnt turn the engine on without an air filter after all that?! the small sponge is just so it doesnt catch dust inside or something. I tested it, i'm not riding it. Quote Share this post Link to post Share on other sites
eyetech Report post Posted March 18, 2016 You need to get a skid plate on there too it is the bottom part of the frame Thats true i'm waiting for it Quote Share this post Link to post Share on other sites
eyetech Report post Posted March 18, 2016 Check the reach (length of threaded part) of the that the plug should be by measuring the thickness of the cylinder head with a bit of hooked wire in the plug hole. It will be about 19 to 20mm. If you are using a short reach plug it could be causing the problems you are having i'm def gonna check that tomorrow, thank you for your help. Quote Share this post Link to post Share on other sites
dadof2 Report post Posted March 18, 2016 http://www.sparkplugs.co.uk/amfinder/?find=spark-plugs-ngk-motorcycle-and-atv-motorcycle-and-scooter-gas-gas-contact-jt25-238-----------------7948683 Quote Share this post Link to post Share on other sites
cbutler Report post Posted March 18, 2016 You will want to take out those bolts holding the rear finder on and replace with zip tyes those finders are costly on any trials bike and getting hard to find for older ones Quote Share this post Link to post Share on other sites
eyetech Report post Posted March 19, 2016 You will want to take out those bolts holding the rear finder on and replace with zip tyes those finders are costly on any trials bike and getting hard to find for older ones Great tip man thank you Quote Share this post Link to post Share on other sites
