I agree with Mark T, the rebuild kit was a waste of money, there was nothing wrong with my original mikuni jets and the ones sent with the kit were way undersized (for an enduro??) seemed to be a generic kit. I did use the jet setter o ring however which fit and seemed to match the original. I don't know how to get this carb any cleaner, carb cleaner, air pressure, etc. Is there a trick to cleaning the pilot jet passage? Also what about the starter/choke plunger, any trick there?
Don't think there is a blockage in the exhaust as it did run briefly the other day, and it was thoroughly cleaned and re-installed with new gasket last spring. New plugs tried and also start fluid used.
There is good fuel flow from the petcock.
Have not checked the right side crank seal however.
Hate to have to go this far but I think I need to check the piston/ring/cylinder.
Thanks again for all your thoughts.

Try cleaning your pilot jet or replacing with new Mikuni.

You said it ran good before it was parked so doubtful it somehow "wore out" while parked?

lolipop50,

I think your right. 70 psi is extremely low on that bike. All 3 of my DT1's have 147 to 152 PSI when doing a simple compression test. I would think 90 psi would be about min on that 250 to be able to start it while kicking it over? I could be wrong. Maybe have some one push you fast and pop the clutch in 2nd gear and see if it lights up. 

As for the choke or pilot jet cleaning, no tricks there. You said you tried starting fluid and it didn't fire or try to start? That pretty much elimanates those 2 things as being the problem. You could take the carb completely off and it would light up with the starting fluid if the engine is able to run. Just be sure the pilot jet curcuit is clean which sounds like you did. Choke is very simple design. As long as the plunger is connected and the lever moves up and down and snaps into place your good.

I don't think the crank seal can pop out of place on that bike because of the 3 ribs in the back of the magneto base keeps the seal from being able to pop out completely. Plus you said it was in place when you did the bubble test?

Very easy to remove exhaust pipe and try starting it to make sure nothing climbed in there and plugged it up. I assume you checked your air cleaner as well? No blockage?

In my experience, a "compression test" is almost useless and can be very misleading unless you have experience with your gauge on your engine (or a nearly identical engine).

Many automotive compression gauges, even expensive ones, can read really low on these engines. And "technique" matters too.

I agree with MarkT 100% on his above comments, not only is the quality of the tools being used a big unknown, the bigger unknown is the person using the tools and the proper technique in using the tools, for instance many people do not know that you need the throttle completely open during the test. I have seen so many people that own a quality digital volt meter but have no clue on how to use it or read it. Many have a cheap volt meter which is usually good for 90% of the things it was intended to be used for, much better is the one MarkT usually recommends a Simpson 260a, I bought mine in the 1990’s for around $300.00 and I still use it quite often, I have seen them on eBay now for an average of about $40.00, they are pretty much obsolete now and is a meter you definitely have to know how to read and use, modern volt meters are like everything else nowadays designed to make us lazier and dumber unfortunately.

Mark,

My experience greatly differs from yours on compression testing, but it easy for me to say as i know my equipment and technique is not a problem for me. I agree though you have to perform a task right to get the correct results. I will give Lolipop50 the benifit of doubt he knows how to perform the task?  

Does the compression feel sort of bouncy on the lever. At 70psi it's feel soft to push through by hand & would likely need a push start to get any joy. Unusual if it was ok when last parked though.

Skydancer wrote:  "Mark, My experience greatly differs from yours on compression testing, but it easy for me to say as i know my equipment and technique is not a problem for me. I agree though you have to perform a task right to get the correct results. I will give Lolipop50 the benifit of doubt he knows how to perform the task?"

Skydancer-  What I said is that technique makes a difference.  And it does.  I'm not and never was questioning or judging Lolipop50, you, or anyone else on their technique.  I was just stating a fact. 

Fact #1:  Different compression gauges can return significantly different results on these engines. (There are factors in gauge construction and design that make some gauges very inaccurate for these engines.  Someone here even posted a YouTube video regarding a Harbor Freight compression gauge and how to modify it to get better results.)

Fact#2:  Technique can also result in different readings.  [Hot vs. Cold.  Kick over vs. push in first gear down a long steep driveway vs towing in gear for 100 yards at 10 mph in second gear. Throttle open vs. closed.  Kick speed (Different people have different abilities)  Auto compression release cable connected vs. disconnected if kicking over... (on models so equipped).  Etc., etc.]

These facts make it impossible to use an unknown compression gauge to diagnose one of these engines accurately from scratch...  or draw solid conclusions by comparing to other people's results if their measurement tool and technique may differ significantly from your own.

That said, if someone has a gauge they've used with their technique of testing they CAN compare THEIR new readings to THEIR past results with that engine or a very similar engine in displacement/porting.

I strongly advise not rebuilding a top end based solely on a compression reading unless you have data with that gauge on that or similar engines.  I know, I made that mistake once on my first DT50.  (On the 88-90 USA DT50, none of my compression gauges, including one made by Snap On, will read over 50 psi. They run great.  I can fairly easily get up over 50 mph on the flat with the little 49cc engines...  over 60 mph if you have a long enough run...  not supposed to run at all with only 50 psi compression)



 

My compression gauge is my foot on the kickstart. You soon know if it's ok or not--just saying. There's a big variation from what's excellent & what won't even start without a push. Sorry folks--carry on.

Just watching Karts down our road on live feed. Big Event. Blimin road is like a racetrack past my gate. Could be dangerous for an old fella wobbling out the gate on a DT1 haha. Track land was part of our farm & where i started off riding on a 125 excelsior hand change, & it survived jumps & my Bantam broke two frames lol. Then Karts leased the land & built a dirt track 60 years ago then developed it from there & bought the land in the end. Million dollar rigs going down since tuesday. Advanced a lot since wheel barrow wheel days & 197 Villiers motors lol, money money. Sorry, shouldn't be mucking up this post.
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