JM09 0 Posted September 2 Couple years ago I bought a big bore kit, got close to it running, and stopped, recently been trying to get it running, bought a new big bore kit, a niche 440, I know they're not reliable but I just want it for now so when this one blows up I'll have enough for a higher quality piston and jug. Back to the problem, I just finished putting it all back together, has 90 psi, good spark, and the only problem I think it is the air fuel ratio or something with the carb, also it popped before the battery died, any suggestions? Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 2 When you say it popped. Did it pop every revolution? Or just once? Did you try starting fluid to see if it pops off on that? Welcome to the forums! Share this post Link to post Share on other sites
JM09 0 Posted September 3 It'll pop every few revolution, I just put everything on it since the left crankcase was leaking oil, but I rechecked the compression, it has about 100-110. It has good strong spark, OEM carb with a new needle and slide, I don't know what jets are in it, but I feel like that might be an issue, but it would pop more frequently when I put the choke on. Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 4 I would see if it starts and runs for a few seconds on starting fluid. If it does it confirms its fuel related. If it doesnt it could be a timing issue. When you did the topend assembly did you make sure piston was at top dead center. Cam lobes facing down. And the auto decompression spring and dowel were in place? (If its a stock cam). Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 4 If this spring and plunger is missing it will never start. The auto decompression mechanism is attatched to the stock cam only. If its aftermarket it will be gone and spring and plunger arent used anymore. But what it does is hold a valve slightly cracked open to help it turn over easier. This isnt necessary on a 400ex at all. Its a carry over from when this engine was kick start in an xr400 dirtbike. Made kicking it over not result in a broken leg lol Share this post Link to post Share on other sites
JM09 0 Posted September 4 Yeah, I made sure the T was lined up, the cam lobes facing down, and made sure it was dead on since the manual chain tensioner moves the timing marks a little, and it has a stage 2 hotcam and when I opened it, I think it was an aftermarket cam already since the decompression pin and spring were already gone, but the cam I have is a bit different as it has a decompression mechanism, but I'll definitely try the starter fluid sometime thursday or near the end of the week. Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 4 If the cam has a decompression mechanism its a stock cam. There is no way to put one on an aftermarket cam at all. And if there is a decompression mechanism on the cam it has to have the spring and pin. If not it will never run. Unless someone took a grinder to the edge of the rocker arm so it cant lift it? But it would also make a heck of a racket just loose on the cam at that point. Share this post Link to post Share on other sites
JM09 0 Posted September 4 It looked something like this, I thought I didn't need the spring and pin, but I can go ahead and order it and see if it'll work Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 4 That is a stock cam. Just not oem. They may claim its higher lift or something. But it isnt. And yes that auto decompression mechanism requires the spring and plunger. It has to catch that to stop it and hold it in place and stop lifting on a rocker arm to hold a valve open. Without that spring and plunger your lack of compression will not allow it to start at all. With the 440 kit you will need bigger jets no doubt. But it will atleast run with wrong jetting. We can go through that process once its started and running. Share this post Link to post Share on other sites
JM09 0 Posted September 5 Alright thank you so much, somebody told me I didn't need the spring and pin, but I'll definitely go ahead and order one soon. Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 5 Absolutely! Always glad to help! Keep me posted on how it goes. Once it starts we can start with tuning it in. I got a pretty good idea of where to start for a 440. Ive built a few. I have even used the niche kit before(not on my personal quads). But It works just fine. 1 Share this post Link to post Share on other sites
JM09 0 Posted September 7 Just put the spring and plunger in, opened the carb and I have a 180 and a 45 jet installed, is this enough for it to run? I'm gonna go ahead and put this rotor and brake in the mean time while I wait for the battery to charge. Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 7 Honestly 45 pilot will be good. The 180 will be lean at wide open throttle tho more than likely. Im thinking you will end around a 185-190. But there are alot of variables. Like altitude. It should idle nice on that 45 pilot for sure. Share this post Link to post Share on other sites
JM09 0 Posted September 7 Alright, I'm at a lower altitude since I'm down in Florida, but I'm gonna go ahead and try starting it now. Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 7 6 minutes ago, JM09 said: Alright, I'm at a lower altitude since I'm down in Florida, but I'm gonna go ahead and try starting it now. Oh yeah down in florida you got alot of humidity also. So that effects jetting aswell as outdoor ambient temp. Keep me posted on how she runs! Share this post Link to post Share on other sites
JM09 0 Posted September 7 Started right up, sounded way better, thank you so much for everything, it took years just to find out that little thing was the entire problem. Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 7 32 minutes ago, JM09 said: Started right up, sounded way better, thank you so much for everything, it took years just to find out that little thing was the entire problem. Glad i was able to help! When you take it for the first ride if you need any help tuning it in let me know! But your gunna be close enough as is to ride it no problem. Share this post Link to post Share on other sites
JM09 0 Posted September 7 Alright, the next problem is that it idles like crap, I have to go about half throttle just for it to barely idle, could it be the jetting or something wrong with the carb Share this post Link to post Share on other sites
JM09 0 Posted September 7 Nevermind, swapped the chinese carb and its idling fine Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 7 2 minutes ago, JM09 said: Nevermind, swapped the chinese carb and its idling fine Ahh yeah. Chinese carbs are junk lol Share this post Link to post Share on other sites
JM09 0 Posted September 8 I meant I swapped the oem kei hin carb I had for the chinese one and it ran, so could just be something wrong with the oem one, ran real nice afterwards. Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 8 Oh yeah oem carb needs cleaned. The china carbs will work fine at first. Then will have random weird issues that can never be explained. Every single one i have ever had has done exactly this. End up being a nice paper weight. Share this post Link to post Share on other sites
JM09 0 Posted September 8 Alright, well thank you for everything, can't wait to go riding once I get some more parts Share this post Link to post Share on other sites
SlammedRanger 1,560 Posted September 8 24 minutes ago, JM09 said: Alright, well thank you for everything, can't wait to go riding once I get some more parts Absolutely. Glad i was able to help! Share this post Link to post Share on other sites
