Here's what I found tonight while tinkering:

*** since it won't start, all compression testing was done w/the motor cold - approx. 65 degrees F ***


I decided to try a compression test again because I don't think I was as thorough as I should've been last night. I tightened the adapter into the plug hole w/a wrench sufficiently tight, solidly hand tightened the hose to the adapter and plugged it into the compression gauge. With the throttle held wide open (this time) I cranked the motor (with the brand new, fully charged battery) until I got my highest reading. Tonight it registered a consistent 75psi. I thought I could see it slowly bleed down but I don't think that was the case - even if it was, there's an interesting reason for it you'll see below.
I then put a clear hose into the spark plug hole and poured in approx. 1/4 capful (from the quart container) of 10w40. I cranked the motor quickly with a rag over the plug hole - nothing got on the rag. I was expecting to see some oil...
I then spun on the compression guage again and gave it another go. Got the same 75psi reading.
Next, I sprayed in some starting fluid. First go at it was about a 3/4 second spray. Didn't fire. Next attempt was about a 1.5 second spray. Still nothing.

Based on these findings, I began to believe that the rings were OK and that we are most likely looking at a valve issue. I spent about an hour or so today investigating burnt valves. Would I be able to get a 75psi reading if I had a big chunk missing from a valve?

Off came the plastic and gas tank to deepen the investigation.

I first spun off the exhaust valve/rocker arm cover. From this end, everything looks great in there. Sufficient oil (now), things look clean and new. On the inside of the rocker arm cover, there was some nasty black sludge which appeared to be burnt oil - not sure if this is normal or not. It was quite thick but would still run when I held it vertically. It wiped right off w/a rag leaving no residue.

*** Also, several times tonight I shined a flashlight into the spark plug hole and cranked the engine. I could see the valves actuating inside and they too looked pretty clean/shiny. It's very hard to tell because things move fast but when I could stop the motor appropriately to take a look at each valve, the small parts I could see looked what I would consider normal. It's hard to tell if the top of the piston is covered in carbon or shiny - I just can't tell by shining the light into that small hole.

After looking into the exhaust rocker arm cover, I tightened it back up and took a peek into the intake side of things. Here's where it gets interesting...
First, the frame and inbetween the plastics is covered with a nice layer of dust. The previous owner said this quad was used in sand pits (in the Northeast - not like CA sand/dessert). The head of the motor has a sandy look to it as well, but I found one on eBay that looks identical. Not sure if that's a fluke or not.
It looked to me like the side plastics either have never been taken off or it's been years since they came off. Same for the gas tank. I closely looked at the heads of any bolts to check for wrench marks and really couldn't find anything. I took this as a good sign thinking that the previous owner either didn't look into this too far or was too lazy.

As I go to put the wrench on the intake rocker arm cover, the damn thing is already loose! Not completely, but an 1/8th of a turn w/the wrench and I'm spinning it off w/my fingers. My first thought was 'here's where my compression problem is!' I took a couple minutes to peer in there w/the flashlight and check things out - same results as with the exhaust side. Plenty of oil and things look shiny and new. I looked very closely at the lock nut on the rocker arm adjust to see if it looked like a wrench had been put to it. I really couldn't tell either way - It looked more like nothing had touched it. Also, there was no evidence of a flathead screwdriver turning the top of the adjuster as well.

I tried to pick up a set of feeler gauges today (because I don't have any) and couldn't find a set down to .002". I'm hoping to get some tomorrow.

*** Also, with each rocker arm cover off, I cranked the motor to view the operation and each valve seemed to operate as it should. From the intake side I could see the cam spinning around and operating. It was we with oil and appeared to be doing its job.

I didn't check clearances or anything like that, so I tightend the cover back on and immediately went for another compression test.
This time I tended to get pretty much 80psi on two attempts. I start thinking that 'if this thing should crank at 60psi, 80psi should get me to fire!' Another shot of starting fluid and NOTHING again!
I didn't have the gas tank on the quad at this time so the two hoses that attach to the carb from the petcock valve (fuel line and reserve fuel line?) weren't connected. I figured I could at least get it to fire from the starting fluid...
As I began packing things up for the night, I noticed that a breather hose from the carb wasn't attached. It was there, but it wasn't attached to the carb. It was about 8"-10" long and just led under the seat area of the frame where it terminated to open air.
I also took a peek at the head cover gasket for the hell of it. There very small amounts of black RTV material in a couple spots but it looks like it's either factory or professionally done and original. The only trouble area I could see was on the front right (when sitting on the quad) in the area where the decompression lever on the 230s would attach - in a little recessed area there I could see what looked like a tiny amount of burnt oil and a small bulge of the RTV/gasket material. It didn't look much like anything (especially considering one of my Quadsports is coated in oil in that area and still runs fine...) but I put my finger over the area and turned the motor to see if I could 'feel' anything - I couldn't.

My next step in this operation is to get the necessary feeler gauges and give a go at checking the valve clearances. I think this motor has the access area where I can just put a wrench on a bolt and crank the motor to TDC and check things out. I've never checked clearances before but did enough research on them to have a good idea of how to go about doing it. My only issue is, if things end up turning out fine (with regard to clearances) or if they're out of whack, I'm not really sure what to do next. I'm obviously losing compression somewhere. It doesn't appear to bleed down according to the compression gauge. I'm guessing the rings are good...?
After checking the clearances, I guess my next option is to pull the head cover and start poking around in there. Any suggestions what to look for?


Here are a couple concerns:
- It's got a Uni filter which seems to be close to a stock unit. The airbox is stock and I've cleaned it all up.
- It's got a White Bros exhaust on it - I'm not sure if it requires/required any mods to the airbox (which didn't seem to happen) or the carb (which I haven't checked) to perform properly
- I'm not sure if the carb was attempted to be re-jetted at any point. Or, if it's gummed up completely. I haven't been looking at this avenue since I found the compression issue
- speaking of compression - is it possible to get an 80psi reading just because the engine is cold? Or should it be much higher/closer to the operating range of the 170(ish)psi - 228(ish)psi?
- Again with compression - is it possible that poorly adjusted valves could yield an 80psi compression reading?
- I don't know if the CDI could be the issue. This is another item I haven't really looked into since I found the low compression issue.


I think I'm getting closer, but we'll have to wait and see.

Thanks to those who have been following along and offering advice and guidance - I certainly do appreciate it. I'm on vacation in 2wks and am hoping to have this up and running by that time so I can enjoy it and not taking the time to fix it!

Take care-

 

Hi Folks,

I was just reading through some other posts and it reminded me of something else I noticed the other day while draining the gas from the tank:

Is the RES position, the gas kind of dribbled out a very little bit.
In the PRI position, it flowed out pretty good - this is how I drained the tank.
In the ON position, I don't recall it coming out at all.

I'm not sure if this may be a downstream indicator of part of whatever problem ultimately contributed to the low compression I'm getting. Just thought this may help round out the entire picture now.

Speaking of pictures, I posted one in the 'ol garage of the new (non-running) baby!

 

Tonight I went out with my newly purchased feeler gauge and gave a go at checking the valve adjustment on this thing.
Please bear in mind that I'm going by the specs in the Quadsport/LT250 Clymer manual as I believe the they're the same on this motor.

I got the motor to TDC and verified play in both rocker arms.

First up was the intake valve. It's super easy to get to on this machine. I slid in the .002" and got resistance. Then tried the .003" and it wouldn't fit. I'm sliding the gauage between the top of the valve stem and the rocker arm. The manual says to slide it between the rocker arm pad and cam lobe, but I don't see how you can reach in that far to do so. Based on the manual, this valves clearance appeared to be OK.

Next was the exhaust valve. It was just a little more difficult to get to but still quite easy. I started with my .005" gauge which didn't feel like I was getting a lot of resistance. According to the manual, this is the upper end of the limit for the exhaust valve. I was able to ultimately slide in the .008" gauge but not the .009". I figured this was where my problem was. After about 8 or so attempts, I got the valve adjusted down so only the .004" gauge would fit. I was psyched to get it to this point and then buttoned everything back up to get a fresh compression reading.

Here's where the trouble started....

I try to spin the compression gauge adapter into the plug hole, but it just keeps spinning. I pull it out and see the tell tale signs that it's starting to strip the plug hole. The adapter literally only has like 4-6 rows of threads - it's super short. The plug still goes in fine, but the upper threads are getting beaten up. I couldn't get the adapter to seat into the plug hole and therefore couldn't get a compression reading.
So, I instead sprayed another shot of starting fluid into the plug hole, spun the plug in and gave it a crank - NOTHING.
Based on some additional reading I've done, I pulled the airbox cover to see what was going on there. The smell of starting fluid came pouring out of the box. I'm not 100% sure if this is normal since it didn't fire, but I'm thinking I may have a timing issue now (at the very least)? Any thoughts?

Beyond that, based on that additional reading I've done, it sounds like I could have a cupped valve due to this thing being run extensively in a sandy environment. It seems as though the stock valves on these and the bigger Z series bikes have a tendency to fail in general and cup easily.
I'm going to pull the head off this weekend and take a close look at things. Maybe I can get some pics to post on here. After that, I'll most likely be getting a new set of valves and figuring out how to install those correctly.

Any suggestions as to what I can or should do about those upper threads in the plug hole?
Any ideas as to what I can do to get an accurate compression reading without necessarily using the adapter that came w/the compression gauge?

Thanks as always for any suggestions/guidance - it is appreciated.

 

A "cupped" valve would result in tight or "zero" lash on valve clearence. You just said the intake lash was good and had to tighten the exhaust side. Not a cupped situation. Haven't seen you say anything about spark. Do you have any spark at the plug? I'm not familiar with the Z250. I have a Z400 and it has an automatic compression release. Don't know if this could "hang" or not, affecting your compression readings. But as posted before 60# should at least fire and run some.

 

Thats a good point, check to see if the compression release lever may be stuck open or partially open. Clean all your grounds, on the battery and anything (like CDI) to frame. Verify there is spark there. Compression test should be done with carb in the closed positon. As long as there is spark, compression, and the cam timing is correct, it should make some sort of fire. Carb may need to have been jetted larger for that exhaust. A 250 cam is a nice performance step up over the stock 230 cam, but it has to be from the correct model 250. Since the cams fit, as long as the bolt holes line up in the heads, they should swap. You may be looking at a top end in the near future, but even with 60 psi, you should get at least some kind of a pop out of it. have you tried spraying a shot of starting fluid in it and cranking with the filter off? If the filter is gummed up with sand/crap, you may not be getting enough air in the mixture, which is why it won't fire, and you are getting a strong smell once the filter is pulled. Is there an emergency kill switch on it? I know some of the electric start versions had the key switch for the start/run, and an additional thumb switch for an emergency situation. Verify they are both on and there is a good hot spark.

 

if you have good hot spark, i'd look into the carb and the fuel valve. after that, ignition and cam timing.

good luck!

 

Thanks for clearing up a couple of items for me guys - I was under the impression that a 'cupped' valve meant it was not sealing properly and allowing air to pass by.

I AM getting spark however, I can't necessarily confirm that it's strong enough - it looks normal to me based on my (limited) experiences with small engines.

I don't think I have a compression release lever on this. There's nothing like what's on the Quadsports. Actually, that portion of the head has a spot to put a decompression piece like on the Quadsports, but there's nothing there.

I'll try to give it a go with the filter off tonight and see what happens. I also get some pics to help show what I'm seeing on this end. Again, my plan is to have the head off this weekend and take a good look at what's going on.

Thanks again~

 

Tonight I just took a couple pics and some short video to try and give you guys an idea of what I'm seeing. I also had a chance to speak with a long time Triumph mechanic today at length. He agreed that it sounds like a valve isn't seating correctly and gave me some ideas as to what to do once the head is off to know for sure. If I can't tell with a simple visual inspection, he recommend turning the head over so the valves are facing up and fill that cavity with Mystery oil to see where/if it starts seaping through. He gave some tips on lapping valves and a lot of info on essentially doing a complete valve job.

These pics are just of the head so you can see the similarities between this and the 230S Quadsports - they're very similar. Also, for those with the bigger bikes, you can see where the differences are.

Top of cylinder head:



Right side of cylinder head:



Left side of cylinder head:



Here's a quick video I put together (29secs) to show it turning over, what the spark looks like and turning over w/out the plug in to see if anything sound out of whack.

YouTube - Suzuki LT-Z250 -- Diagnosing starting problems

(not sure if I can embed the video here - if not, disregard the long link below...)

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/SBBecbEXQMA...</param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/SBBecbEXQMA&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>



Let me know what you think.

Thanks as always!

 

Spark looks nice and white hot from what I can tell. Pull the head, and set it up on end so the exhuast port is facing up. Fill the port with mystery oil, water, mineral spirits, whatever you want. Watch the valve and see if it begins running out, or if it just slowly weeps. A good valve will not alow anything though. If it's running out, you have a bad valve/seat. Gentle weeping can be cured by lapping. Do the same for the intake side as well. As long as you'll have the head off anyway, why not hone and re-ring it at the same time to eliminate a compression issue from the equation as well?

 

Thanks for the suggestions on this. I'm going to try and find time to pull the head today and take a look at things. I'll try and get some good photos too. If nothing else, maybe it can help somebody in the future diagnose similar problems on this or similar engines.
That's a good idea to hone and re-ring. Only problem I have in my area is that nobody really stocks these basic parts - I need to order everything online. I haven't gotten rings yet because I want to check out what size piston is in there in case it's not stock.
I'm planning to get rings, a top end gasket set and a carb rebuild kit due to signs that it sat for a while. If the valves are toast, I'll get a set as well. Any recommendations when replacing valves? Is it an involved enough job where it's worth doing additional work and/or upgrading? I'm not really sure if I need to get new seats, guides, springs, etc or if they can all be re-used.

Assuming all goes well, I'll have a handful of photos up with a post tonight.

If you're here in the Northeast, enjoy a beautiful day of riding - what a nice day!