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Hi all!

 I've got an issue, one of many when it comes to bikes. I searched throughout all the pages I could find pertaining to my situation and couldn't find very much useful information.
So the issue is, the bike has no electric start.... until it's hot enough to melt steel that is. It will bump start first time every time. But I can sit and crank the starter over for ever and it'll never start until the charger is bumped up past 200 amps. Not good.

 The story so far,
Got the bike for 1k cash. Guy said it has no spark and no second gear. This particular guy also only ever rode newer crotch rockets. Brought it home pulled the choke, attached battery charger and she fired right up. Ran like absolute crap, but oh well I figure it's an older bike with only 10k miles so it probably needs a good carb cleaning. Took the carb apart and didn't know I messed something up until way later(didn't tighten down main jet). Oh well she runs well enough if I can get her started. Moved from California to Oklahoma. Eventually found the money to fix 2nd gear, and as I am a certified Honda small engine technician apprentice I figured it would be no big deal. Completely tore down engine to it's roots replaced 2nd, and 5th gear(because 5th gear connects to 2nd on the countershaft) dogs were worn pretty badly on both. The engine looked quite good compared to most others I've seen. Put the engine back together as per the service manual. Did all the right steps including loosening the banjo bolts to test for proper oil pressure. I even tore apart the electric starter to clean the contacts and the brushes and replace the dielectric grease. Adjusted the valves as per the service manual, replaced all gaskets, o-rings, seals, and oil filter.
 Finally after about a month of waiting on parts and reassembly I get to start her, only she doesn't. Electric start is still giving me the same issues I've always had. So I replaced the Ignition coil, CDI box, and put a new battery in, plus the starter motor rebuild. Nothing. Still cranks forever. I said what the heck and tried to push it slightly down hill and bump start it, and voila... fired right up! Once she gets hot enough and the stator charges the battery enough it'll electric start... sometimes.
 So I looked towards ignition, used a tool called ignition mate. Pretty awesome tool if you can afford it. Well while cranking the ignition mate reads the spark plug is getting 1-4kw of "spark" every cycle, well it only fires after getting up past 5kw sometimes 6-8kw. And sometimes the ignition would be intermittent as in it wouldn't give any spark at all. I cycle the ignition and it seems to soft reset the bike as it will usually give it back spark. I tested this with the new and old CDI box, the old one would never spark. Ever. So I threw it in the trash. A month later I stil l can't figure it out.
 Is there something I'm missing?

TL;DR
Bike won't start using electric start only bump start before and after engine rebuild
Electric start works after pushing the starter past about 200 cold cranking amps or when hot.



 

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Probably too much of a voltage drop to the CDI.  They won't fire below a certain voltage (11 is the general rule of thumb)  and something in your starter system sounds like it's pulling the voltage to the CDI below that threshold. 

You can jump power from another good battery directly to the CDI power input and see if the problem is solved.  If so, then chase down the problem.

Edited by Hollerhead

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You said that you put in a new battery, but what kind?

I have a Yuasa AGM because I know it's one of the best lead-acid batteries that I can get.  Had those in both of my bikes until I got the new KTM.

To get the bike to start right away when cold, you need the right pilot jet, the right setting on the mixture screw, and a correctly working choke.  And it seems that each bike is as bit different on the settings that it needs before it will start.  Mine wants full choke to actually start but is immediately happy with half choke and I can turn the choke off right away once it takes a throttle blip and runs clean.  When it's 65 degrees or warmer, this is immediately.  It's colder now, so I'll have to go check how long it needs to warm up first.  Never more than 20-30 seconds.

Can you describe what it needs to get it running when you bump start it?  Specifically, what do you have to do with the choke when you do that?

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 It has a powersport specific battery that gives 120 CCA, I tried a different battery as you said from a V-star that gives 240 CCA. And same thing, the motor spins a LOT faster but no fire.
 To bump start it I turn the fuel and ignition on, put it in 1st gear then I just run really fast jump on a dump the clutch. After a half second or so with the throttle held slightly open it fires.

For some reason the PO put an aftermarket carb on, it's a Mikuni flat slide type with no other markings on it looks like a TM series, but I already tried putting a larger pilot jet in it, I went up 2 numbers on it and it didn't change anything. Messing with the mixture screw while it was running I twisted it all the way in until it started to sputter, then back all the way where it was supposed to sputter but never did, even like 12 turns out or something. So I just left it at about 1 1/2 turns out. And I have never been able to start the bike on choke except the first time I brought it home.

When I was doing electrical testing I first ohm'd out the battery to the starter, then to the CDI box, and all was fine. No shorts or opens. The battery drops to 11.47 at the lowest when cranking until it loses voltage then it drop down to about 8-9 volts. I just charge it and it comes back up. While running the battery goes to 13.04 and when at WOT it jumps to almost 14.

Update, I just tried bump starting it when it is 37f outside and it wouldn't go until I choked it.

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I can't offer any additional help if you don't have the stock carburetor.

But I'm surprised that you can bump start it in first gear.  Mine will just slide the tire in first or second gear even if I'm bouncing on the seat at the time.

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Quit beating your head against the wall. Get a REAL factory carb. Not a look alike off eBay. Will save you a lot of time and money. 👍 PS just go to Sudco and order it. No question it will be real.

Edited by mirage100

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20 minutes ago, mirage100 said:

Quit beating your head against the wall. Get a REAL factory carb. Not a look alike off eBay. Will save you a lot of time and money. 👍 PS just go to Sudco and order it. No question it will be real.

If I'm gonna get a new carb I would buy a Lectron for it. But it's not a chinese knockoff I know what Mikuni's look like. Idk why the PO put a different one on in the first place, maybe because the stock one something was wrong? but I don't think it's entirely a carb issue because it idles and rips just fine once it is started.

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Seeing as you say you are a Certified Honda Technician....a compression test should be no problem.

Enter results here please >

 

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It's not your carb and if it's a pumper , it's better than a Lectron. Look at the Mikuni pictures at Niche Cycle and see if you can identify it. If it is a pumper , it's likely a TM40-6.  Niche will also show you the OEM jetting it came with , which is pretty close. They also have parts , if necessary. It sounds like you've got a battery issue , that won't let it spin the starter fast enough unless the bike has just been running and charging it. Your voltages running are normal , but the drop while cranking drops too much , too fast. 

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So, could it be the starter and the battery? I'll try another new battery tomorrow, but the starter has always been slow.

What are the signs of a pulse generator not working correctly? As in tell tale signs. I'm trying to rule out every little thing I can. I'm also gonna re check the valves tonight as well because I think that when I did the rebuild that I adjusted them while the engine was still warm.

 

Update, I looked at some pictures and am fairly certain it's a TM38-27, which is a flat slide. Not a pumper. 

Stock settings are #230 main, 22.5 pilot, and 6FJ41 needle jet. The only thing I have changed to try and fix it was changing the 22.5 to a 27.5 pilot jet. Everything else is the same.

Edited by photonicreno

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So I checked all the valves again last night, the only one that was out of spec was the right front exhaust valve, it was at .008" supposed to be .005" so I adjusted it down to spec. Put everything back together and still no fire. Tried cleaning the kill switch contacts and once again, nothing. The battery is a Shorai powersports battery. I have no clue if it is lead-acid or lithium or whatever else.

What else can I check?

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intermittent spark,,but will always fire/start with a push start almost always is the pulse generator..

you push start it and the engine spins faster than the starter ever could even on a new bike ...the faster the spin the higher the voltage from the pulse gen..

pulse gens break down in these bikes with age/mileage cause low trigger voltage to the CDI..

 

B

 

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