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Discussion Starter · #1 · (Edited)
hi as i posted in wrong section been sent here ty jazzy.im having problems with my cbr400 rr 1988,she used start first time that was before we had some good winter weather, now she just wont start iv checked starter coil the fuel pump relay etc they seem fine i checked carbs an wiring an they seem fine the battery seems be holding charge fine only thing i have noticed when checking the spark plug the spark is weak an jumps to the side which im sure isnt right,so im wondering would be best to replace the ht leads an coils only problem im having is i can only find nc29 ones on ebay my baby is a nc23, would it be possible to use nc29.any help would be much appreciated an im lost at mo
 

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R1ckster, from what you're describing it sounds like you have a short. That would certainly weaken the spark and reduce the chance of a start up. You've not said where the short is happening so it is difficult to offer any meaningful solution. But what I would say is that these bikes don't really appear to have a good, strong spark when testing at the best of times. That said, the short (I'm guessing) is only on one plug, so you should at least be hearing the bike trying to start with the occasional back-fire.

If not, your problem probably comes from the battery. It's usually a lack of power in the battery that causes the bike not to start, even when it sounds like it's turning over strong. If those starters aren't turning over at warp 9, the bike is a pig to start. I would start by recharging that battery over night (which will give you time to fix the short) and have another go in the morning.
 

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Discussion Starter · #3 ·
thanks for ur reply surffrog,iv checked all the plugs an its same with all of them the spark seems jump to side of the plug.u are right bout the bike trying to start an yes it somtimes back fires, we had battery on charge it seemed fine but then as i said it did seem ok that was before the big freeze an snow after that she just didnt seem wana start when she did she ran for few mins then back fired,im not sure where to start looking for a short iv checked the wiring an earth connections etc but they seem fine but maybe im missing somthin any other advice would be great, thanks
 

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thanks for ur reply surffrog,iv checked all the plugs an its same with all of them the spark seems jump to side of the plug.u are right bout the bike trying to start an yes it somtimes back fires, we had battery on charge it seemed fine but then as i said it did seem ok that was before the big freeze an snow after that she just didnt seem wana start when she did she ran for few mins then back fired,im not sure where to start looking for a short iv checked the wiring an earth connections etc but they seem fine but maybe im missing somthin any other advice would be great, thanks
Well, if you are seeing the "short" jump from the plug to the wall of the cylinder, I would say that was the issue. At this point I've got to think that maybe the cold snap has broken-down the insulation in the HT leads... Odd that it would do it to all four though.:huh:

I'm only guessing here but, when you say the spark is jumping, do you mean when you've got the plug out and are earthing the end of the plug to test? If you are saying that, then all that means is the spark has found a closer earth than the one you think you have provided. Either way, I would suggest you change or clean the ends of the HT leads as well as the plugs.

That doesn't get you closer to a solution but does mean we don't have to work back though the whole circuit. I would look to the battery charging circuit as the possible cause. When the stator's stopped functioning at full power (they return little enough charge back to the battery as it is), you will be putting greater drain on the battery than normal. You kind of indicate that by saying that after a charge it worked okay but for only a couple of minutes.

Also, if you have just changed your light bulbs to a more powerful set, I would change back. The charging system on these bikes (as I said before) is naff. After changing mine I went through all kinds of starting grief. One way to test for this being the problem is by disconnecting one of the head lights and trying to start up. If it starts you know you're not getting enough power to the starter.
 
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