Motor problems => got questions

[troybilt]

Well, I thought I wasn't getting spark so I replaced the coil and CDI. Now I got spark but no GO. I checked the compression and is anywhere bw. 140-150 psi. It should still start even if the compression is low right? It just doesn't even come close to starting. Its got good fuel and spark plug is brand new and little wet when I remove it so I know I've got fuel getting to the cylinder. I've even tried the ol'-carb cleaner spray into the top of the cylinder. Whatcha all think?

Tell me its not time to rebuild, fk-me.

[8686]

Ok ok...never mind.

[Jason Hall]

Crank Seals??

[312R1]

Sparks engine...;)

[86 Quad R]

140-50 seems a bit weak. did you hold the throttle wide open when checking the compression? is this a fresh engine? what head gasket configuration are you running?

there is a remote possibility that the crank case is puddle'd with fuel/mix is is somewhat flooded. try holding the throttle wide open(with choke off) while starting to help flush it out or remove the spark plug and do the same procedure and afterwards reinstall the plug and try again but what ever you do..... DO NOT POP START IT!

[Saul76]

Have you checked your woodruff key? Not sheared is it?

[troybilt]

I should mention this is a a cherry 89 motor 100% completely untouched since 89 and ran fine until now, but has been a bit tempermental lately as far as starting I had trouble last March similar to this, but pull started it with my RZR at the time... whether I should've of done this or not, I don't know, but it did finally start then and had no problems that weekend at the dunes.

No I didn't hold the throttle wide open when checking compression. Should this be done?

312R, I may still hit you up on that engine. :D

Anything else I should check?

motor Mods, FMF SST pipe, 38 airstriker, boysen rad valve, k&N filter no lid. it is Jetted properly before someone asks...

My thing is when I kick it over, there isn'd even a glimpse of hope to start, just seems dead.

When do you know its time for a top end? I'd like to keep this one stock, I plan to restore it eventually. It doesn't need much to finish it.

I appreciate the help. thanks. Troy

[Honda 250r 001]

what do the reeds look like? the head isint cracked or something is it? leaking head gasket?

[machwon]

Sounds like you have spark and fuel, that leaves compression. Normally I say a motor that takes 3 kicks to start is getting weak. Needing to pull start it is another good sign.

[troybilt]

Yeah, I'm thinking its compression. Rechecked spark and fuel, both good.

Here's the run down what I did with the compression tester, you tell me if this is right or wrong:

Threaded the tester into the sparkplug hole and made sure it was a snug fit. w/No, throttle... kicked it over, however, it took 5-6 kicks to build to up to 140-150 psi. How high should compression be on first kick? It was consistently 85-90 on first kick.

I also checked the reeds, lastly, and f'd up the gasket, so now I need to locate a gasket. I think I'm going to freshen up the top end. 1st overbore and go from there.

Been about 15 years since I did a top end and that was on my KX125. So where's a good place to get a new top end set? Any recommendations?

[Saul76]

Originally posted by troybilt
Yeah, I'm thinking its compression. Rechecked spark and fuel, both good.

it took 5-6 kicks to build to up to 140-150 psi. How high should compression be on first kick? It was consistently 85-90 on first kick.



You got spark, fuel and 150lbs of compression - that engine should start.

Did you check to see if your woodruff key might be possibly sheared?

Have you checked your silencer to make sure it isn't plugged?

150lbs might not be 'high' compression but IMHO enough to roll that engine. I'd hate to see you rebuild the top end only to finish and still have an engine you cant start.

[norcalduner]

Hey Troy, if you know for sure that .....

1. you got a good fat blue spark
2. fresh fuel and correct premix
3. clean, unplugged air filter

I would pull the head and put a thinner head gasket, put it back together and see if it runs. This is a QUICK and CHEAP option to isolate/eliminate your doubts of having a low compression issue. Keep us posted.

[86 Quad R]

you are sposed to kick it over till the needle stops with a WOT. :cool:

[troybilt]

86 Quad R, I'll try with WOT and report back.

Ever heard of squirting a little oil in the cylinder, crank it a few times and them try to start it? My pops said they'd done that on cars and other engines in past. Said the oil helps seal the rings and gives a little more compression to see if it starts, then if it does you know its compression issue....

Saul, I agree I'd hate to rebuild if its some random issue that will still be there afterwards too.

[IcutMetl]

Even when at 150-155psi, my engine still started on the first or second kick. Check on ebay for pistons. I was able to find a new Wiseco 67.5mm piston with rings, needle bearing, and gaskets for like $153. Probably would be able to find a smaller piston or a Pro-X cheaper. I don't think I paid but $35 or so to have it bored/honed.

[Honda 250r 001]

Originally posted by 86 Quad R
you are sposed to kick it over till the needle stops with a WOT. :cool:

yep if you didnt do this the first time your reading will jump. when i did it on my 250r with out the throttle wide open, i got 90 comp, with the throttlw open, 195. haha its a big difference. So i think your comp will be good.

[troybilt]

OK... I'll give it a try before I go to any drastic measures... :macho