1985 Honda XR250R spark issue problem

[buffalorider]

Hi folks. Just FYI, I did do a search on this subject and found nothing so decided to post the question. I have two of these 1985 250 XR's and both have the same problem...no spark. I am wondering if anyone knows the correct ohm readings for the alternator/stator test, the pulse generator coil test, cdi test and coil test and more importantly, the procedures to test them? I have swapped out all the parts (except the pulse coils) between the two bikes and still nothing. The stators "look" good. I am leaning towards it being the pulse coils on both bikes but what are the odd's? Tried Google with no luck on any worthwhile information. Thanks for any help. Sure would hate to part them out on fleabay but may need to. Pulse coils are hard to find and ain't cheap!!

[daytripper72]

I'm sure this isn't the answer you're looking for, but I have a 1985 Xr250r I was having issues with the engine to so I put a Stroked out Xr200r Engine in the frame. Any year XR 200 will fit right in. They are easier to work on and parts are readily available. And you can find xr200r engines for pretty cheap.

 

 

 

[Trailryder42]

I have the '86 figures and procedures but don't know if they'd be the same for the '85. See if you can locally find a Clymer manual on the '85.

I wonder if places that rebuild starter motors could refurbish a pulse coil.

Is this problem a recent development? Those bikes look like they've been refurbished from the ground up.

Wondering the history and how you determined that it's no spark you're having a problem with and not something else.

Edited April 28, 2017 by Trailryder42

[buffalorider]

Those bikes in the photo belong to Daytripper, they are not mine. Pulse coils are sealed units. Clymers manuals do not give ohm resistance readings for them from what others have told me. Don't want to buy the book for nothing. Figured if someone had them already from a service manual, they could send them in a PDF. Hard to believe I did not get any answers on this question from this forum. Bummed now.

[buffalorider]

On 4/28/2017 at 0:14 AM, daytripper72 said:

I'm sure this isn't the answer you're looking for, but I have a 1985 Xr250r I was having issues with the engine to so I put a Stroked out Xr200r Engine in the frame. Any year XR 200 will fit right in. They are easier to work on and parts are readily available. And you can find xr200r engines for pretty cheap.

 

 

 

No, not really the answer. Pulse coils for those engines as well were the same and also hard to find.

[FFMan]

i thought i had this problem on my project bike, until someone on the forum pointed out that the spark isn't the strongest, and you'll struggle to see it in daylight.

have a look at dusk or night, it might be there - mine was but i was dubious the weak spark would work under compression, but it fired up 2nd kick.

i checked my parts against the book but i couldn't get the stated resistance reading on the scondary side of the coil. I tried 2 and both were the same but both worked.

I can post the correct readings for the stator and pulse coil later.

The basic wiring is as per the attached, so yo ucan check it through

[buffalorider]

Thanks! My wiring is in tact and ground is good. I have two of the exact same bikes so tried swapping out CDI's, coils with no luck. I really need to test the ohm's to be sure. I'm fairly certain the ohm readings were similar on these mid 80's bikes, so even if yours is a different year, it may tell me if my electrical units are totally shot or not. I may also try the additional ground wire from the head to frame mod to help ignition. Thanks for getting me that info, I will check back later today.

[FFMan]

1985 seems to be something of a crossover model but best guess specs are:-

 

Pulse gen coil 460-580 ohms

coil 1984-1985 primary 0.16-0.19 ohms

                        secondary  3.69K-4.51K ohms

Coil 1986- secondary with spark plug cap removed 3.7-4.5k ohms

                                  with spark plug cap on 7.4k - 11k ohms

Alternator (black/red wire & green wire)  50-250 ohms

i couldn't get any secondary side readings for some reason but mine works.

[buffalorider]

Excellent I will try these. Are most of these just touching each wire to each ohm tester lead? 

[FFMan]

yep just connect the meter to each lead. Obviously don't hold both with your hands otherwise it will affect the readings.

if you don't have an alternator green wire, just use a good ground on the engine.

[daytripper72]

Hey FFMan.. trying to remember if the 84 85 xr had the resistor in the spark plug boot. I seem to recall having to remove one on an 85 cuz it was bad causing no spark.

[buffalorider]

Yes they have resistor's in them but have previously been removed and a small copper rod was installed to take their place. Good or bad??

[daytripper72]

I have removed them and used steel springs in place, about the diameter of one you would find in a ball point pen.. that could be the culprit.

[daytripper72]

 

The copper could be corroded too.

 

[buffalorider]

FFMan, At first I was getting weird readings. I got a .468 on the pulse generator and was not sure if the decimal point was correct or not. Primary coil I was getting .2-.3 and figured that was higher than the .16-.19 your book says but still figured it might be OK for my 85. The secondary coil measurement (taken with one lead to the plug end and the other to one of the metal tabs on the coil) at first read nothing (overload) so I stuck one of the leads into the plug lead wire itself and with the resistor in the cap it would read 15.00k ohm's. When I took the resistor out and just used a copper rod of the same size, it read a nice 4.29 ohms. The alternator read .328 so I felt I had good readings....but I still has no spark. I tried to pull start it with a friend on my quad and still nothing. Now I was leaning towards a bad CDI. BUT...I decided to run a jumper wire from a 8mm head bolt to the frame and the damn thing started!! Not sure where the bad ground could be as I checked everything over. It still runs like crap but I think that is gummed up carbs.

So, being the mechanic that I like to think I am, I can easily take apart the carbs and clean them, but to me it looks like a nightmare taking them off the bike. What are any secrets to their removal? Do I have to remove rear shock to then remove the air box straight back and then pull the carbs to the rear? I certainly hope not. Please advise. Thanks!

[Trailryder42]

A lot of folks, instead of removing the airbox, take out the subframe bolts and just swivel it up out of the way, bringing the airbox with it once you loosen it from the carb. But pictures I'm seeing looks to me like the frame on those year models are all one piece. Bummer.

If you can get the float bowls off with the carbs on the bike, then you have access to the jets. If you can get the fuel screw assemblies out without losing anything, that would go a long way to making them run right to clean those passages.

Otherwise, removing them from the bike is going to be in order. Because it's such a bitch to do is the best reason to use stabilizer in your fuel when the bike is going to be sitting for very long. Along with draining the float bowl.

[daytripper72]

Glad you got it started! You can either bend & stuff the intake boot outta the way or unbolt the boot from the air box. The dual carbs are a pain to remove but doable.

[buffalorider]

8 hours ago, Trailryder42 said:

A lot of folks, instead of removing the airbox, take out the subframe bolts and just swivel it up out of the way, bringing the airbox with it once you loosen it from the carb. But pictures I'm seeing looks to me like the frame on those year models are all one piece. Bummer.

If you can get the float bowls off with the carbs on the bike, then you have access to the jets. If you can get the fuel screw assemblies out without losing anything, that would go a long way to making them run right to clean those passages.

Otherwise, removing them from the bike is going to be in order. Because it's such a bitch to do is the best reason to use stabilizer in your fuel when the bike is going to be sitting for very long. Along with draining the float bowl.

These are 1985 models with no removable sub frames and have dual carbs. Just wondering what the manuals say the steps are to remove them before I start to dig in. These were also not my bikes and bought them this way. I agree with using stable but even that stuff doesn't always work in small orfices, etc. I just try to run the carbs dry and then drain the bowls. 

[buffalorider]

3 hours ago, daytripper72 said:

Glad you got it started! You can either bend & stuff the intake boot outta the way or unbolt the boot from the air box. The dual carbs are a pain to remove but doable.

Thanks. In looking at the schematics above, I noticed the harness is grounded to the frame in an additional spot other than by the coil. THAT is the wire I cannot find on this bike (yet) and could be the culprit. I have seen on others it is grounded near one of the air box bolts to the frame but not on these 85 models. Still need to find that wire!

[Chuck.]

On 5/3/2017 at 7:30 PM, buffalorider said:

..............I decided to run a jumper wire from a 8mm head bolt to the frame and the damn thing started!! Not sure where the bad ground could be as I checked everything over. It still runs like crap but I think that is gummed up carbs.

So, being the mechanic that I like to think I am, I can easily take apart the carbs and clean them, but to me it looks like a nightmare taking them off the bike. What are any secrets to their removal? Do I have to remove rear shock to then remove the air box straight back and then pull the carbs to the rear? I certainly hope not. Please advise. Thanks!

Engine to frame bonding can be a problem on old bikes and restored bikes with freshly painted frames. I now run a jumper wire from the cylinder head to the frame ground point on all of my XRs. And make sure the frame ground point has bare metal.  I had one that developed hard starting; the frame ground bolt was loose.

I found the easiest way to remove the carbs was out the left side with the manifold attached. reverse for install.