de comp out and has wicked low compression and smoke a lil

[ridein'red7]

well iv asked before and its been a while but i bought my wheeler as a basket ad build it up. well its now a 416 10:1 cam is stock but has the decomp lobe off and welded oil port, ported and polished, and alot more but i lost the spring for the decomp so i took the plunger out would this cause it because it is just a open hole?

[honda400ex2003]

if there is no decomp bot the spring and the plunger should be out before riding it. Im not sure if that is your question completely but yes there is just a hole then. steve

[hocman123]

ok if u just rebuilt it and it has really low compression and smokes then i think u did something vary wrong on the rebuild. not really sure what. but the hole is just a tiny empty hole that no oil or compression could leak from so that is deffenattly not the problem

[CJM]

Pistons in backwards?

[bherriman]

Originally posted by CJM
Pistons in backwards?

I could be wrong but I think they still have compression when the piston is in backwards. I'm leaning towards an incorrect bore size, or an out of round bore. It seems to me that if its a fresh rebuild and it has no compression somethings has to be wrong in the piston/cylinder department.

[CJM]

Originally posted by bherriman
I could be wrong but I think they still have compression when the piston is in backwards. I'm leaning towards an incorrect bore size, or an out of round bore. It seems to me that if its a fresh rebuild and it has no compression somethings has to be wrong in the piston/cylinder department.

I would agree, but without seeing it its kinda hard to tell.

Could be improper ring setup, bore issues, IDK tbh.

[hocman123]

he might not have broken it in good and the rings didn't seat well thats what i think.

[ridein'red7]

possible wrong bor esize but a machinst for 40 years did it and i dont thing thats the prob but itll run if u push stat it than its runs and hangs wid a 450r with no smoke untill warm but when i try to e start it when cold it wants to fire but it wont

[bherriman]

If it is running with a 450, its got compression. What makes you think compression is low.

[CJM]

If its push starting and hanging with 450s then it doesnt have a compression issue.

Throw some jumper cables on it, betcha the battery is shot.

[the Z Man]

If you take out the spring and plunger you have to remove the part on the cam.... will not start...

[hocman123]

he did he said it in the first post but its a little hard to read

[the Z Man]

didn;t see where he pressed off the lobr from the cam

[ridein'red7]

the lobe is pressed off. 2 comprssions gauges right off the snap on truck get the same reading at cold 30 lbs-40lbs and with a new battery it just turns over and over and over

[bherriman]

How are you doing the compression test?

[hocman123]

Originally posted by ridein'red7
the lobe is pressed off. 2 comprssions gauges right off the snap on truck get the same reading at cold 30 lbs-40lbs and with a new battery it just turns over and over and over

that has to be wrong 30-40 psi that think is not going to start no way no how not even push start u should have no less then 100-130 psi and if ur in the low 80s it would stop running. plus u said it would hang with 450 so compressiong i am sure is ok.

how did u break in the engine???

and did u replace all the valve seals and re lap them???

but it is most likely the starter not canking well if u can push start it

[CJM]

Attach comp gauge, crank motor over for about 3-5 seconds. It should at least be 100psi if not greater.

You cannot have low compression if you are running with 450s fine.

Like I said, have you tried hooking jumper cables to the battery and seeing how it cranks? Push starting it works, thus Im betting the battery is bad.

[bherriman]

Originally posted by CJM
Attach comp gauge, crank motor over for about 3-5 seconds. It should at least be 100psi if not greater.

You cannot have low compression if you are running with 450s fine.

Like I said, have you tried hooking jumper cables to the battery and seeing how it cranks? Push starting it works, thus Im betting the battery is bad.

I believe you hold the throttle wide open also.

[CJM]

Originally posted by bherriman
I believe you hold the throttle wide open also.

You are indeed correct sir. Also a good idea to have the killswitch on so it wont turn over. Manual wants you to let it run and warm up then kill it and do the test but it will be roughly the same without doing that.

[MtnEX]

Yeah, you are not holding the throttle open... or your filter is clogged... or your starter just isn't turning it over fast enough.

[ridein'red7]

i sorry guys this thing has giving me head aches from a expirenced mechanic, iv been stumped thats why iv been so fraustred and i put it in the barn for a while, and im doing the check wid the throttle wide open , used two new gauges same reading, push start it and give it two shots of throttle and its blurps and burps and boom fires rite up and revs out and everything. thats why i was wondewring if it was decomp. i broke the engine in with non sythic honda oil, went easy around the track at my house with slow increased amout of gas, and cooled it in front of a fan that did the same than rode it normal but no pinning it. iv been pulling hair with this. and its hauls assss too wheelies all gears. smokes till warm to

[hocman123]

well smoking to it gets warm is not really bad but i think ur problem is in the starter, coil, silenode or the battery. and just b/c it new doesn't mean it is not bad it would be the first one to have been bad out of the box.

[bherriman]

Originally posted by ridein'red7
i sorry guys this thing has giving me head aches from a expirenced mechanic, iv been stumped thats why iv been so fraustred and i put it in the barn for a while, and im doing the check wid the throttle wide open , used two new gauges same reading, push start it and give it two shots of throttle and its blurps and burps and boom fires rite up and revs out and everything. thats why i was wondewring if it was decomp. i broke the engine in with non sythic honda oil, went easy around the track at my house with slow increased amout of gas, and cooled it in front of a fan that did the same than rode it normal but no pinning it. iv been pulling hair with this. and its hauls assss too wheelies all gears. smokes till warm to



Its probably smoking from improper break in (basically ride it like you stole it), but if it will push start and run like you say it does I can't imagine it having only 30 pounds of compression. It seems impossible to even run with that low of compression. I find it hard to believe it has anything to do with the decompressor. After market cams don't even use it.

[CJM]

Im gonna ask this one last time!

Have you hooked up jumper cables to the battery and tried starting it? if it turns over your battery is toast!

Betcha your valve seals are shot too, typical smoking till it warms up.

[MtnEX]

Well, if you are sure your timing is right and you are holding the throttle open, it's not turning the motor over fast enough.

I don't think it is possible to have 40PSI and run with this motor... especially considering it no longer has the decompression mechanism.


Try again with jumper cables... and double check the intake to make sure you didn't leave a rag in there somewhere while working on it and put it back together without removing.

[MtnEX]

Where you located ridein'red7?

Maybe I or someone near you can drop by to observe the problem.

[ridein'red7]

timing is set at tdc and cam lobes down so the marks are lever right on the dot, i think i found my problem, my cylinder bore is 87.3 and should be like 87.1 so the rings are expanding when they get warm i think

[sixer3]

I've read through this a few times and still don't understand what you are saying...

-RIGHT NOW, are you able to go out and start it?

-RIGHT NOW, are you able to go out and"wheelie in all gears and hang with 450's"

Your cylinder bore is within spec I think.
Not sure what you mean about the cam timing.

-Your piston is at TDC twice, once on the compression stroke and once on the exhaust stroke. On the compression stroke and flywheel timing mark lined up the 2 horizontal marks on the outside of your cam gear should be parallel with the surface of the head.

- | - (marks on cam gear)
____ (top of cylinder head)


let us know exactly when all of this started happening. Has it been like this since you first rebuilt it? Was it doing any of this while you were racing those 450's? or is it more recent?

[ridein'red7]

sorry i do this from a cell phone its hard to write haha. flywheel is lined up with "t". if i push start it and let it warm up itll go fine but idles high than itll bog way out and have to give it gas

[MtnEX]

The "T mark" can be lined up at top dead center of the compression stroke or top dead center of the exhaust stroke... just so you know.

Line up the T mark and check to make sure you have some play in your rockers. If not, roll it over to the T mark again. Check again, and when you have it, then check your valve clearances and cam timing.

I find it is easier to line up on the wrong stroke... because of the way the engine springs on over (passes proper alignment in the process).

[ridein'red7]

could valve be to tight? just have though about it

[sixer3]

Honestly sounds like a timing/valve issue.

check your cam timing AND valve clearances keeping in mind the information we posted on page 3 and let us know what you find.

If that isnt it, we can go from there