Suzuki DT55 limp mode? Low RPM's

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

Okay so I have the oil tank, silencer cover, carburetors, carburetor inlet cases and reed valves out for all three cylinders. Bits of metal are evident in the number two crank case, some pieces slightly smaller than a dime, and oval in shape.

Does anyone have words of wisdom for me regarding unplugging these maddening electrical connections? It seems I need a tool that pushes three tabs down simultaneously in order to pull the connections apart - very frustrating. Cheers.

EDIT: I figured out the electrical connections.

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

Well, back at it. Pulled the power head off tonight ... think there are enough wires on this thing!!??

Sheared 5 of the 18 bolts when removing the exhaust cover. Sheared 2 of the 5 head cover bolts (not head bolts) when removing the cylinder head cover. Bad bolts or over torqued once upon a time. Hopefully a machine shop can get those out for me.

So far all I have found is pitting along the crown of the top piston. All cylinders are in really good shape, no scoring or pitting. I'm starting to suspect lower end damage (connecting rod/crankshaft/bearings) ... But what accounts for loss of compression?? Keep digging I guess!! Anyway ... If anyone is out there, just keeping you all in the loop. Will post pictures when I find something.

 

[mphelle8vld]

Re: Suzuki DT55 limp mode? Low RPM's

Shearing off those bolts is pretty common, I'm still going with the rings being pinned by a damaged middle piston. Where you able to idenify the metal you found in the crankcase?

 

[99yam40]

Re: Suzuki DT55 limp mode? Low RPM's

Bits of metal are evident in the number two crank case, some pieces slightly smaller than a dime, and oval in shape.

What are they made of?
aluminum?

maybe piston skirt if aluminum

pics of pieces and top of piston would be interseting

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

Ask and you shall receive!

There is a photo of the piston crown, top cylinder. I haven't had a chance to pull all that apart yet.

Here are the metal pieces pulled from #2 crank case. Maybe some of you can tell what kind of metal they are?

 

[99yam40]

Re: Suzuki DT55 limp mode? Low RPM's

top piston looks like something bounced around in it or was it just damage from overheating along exhaust port
But that cylinder had good compression?
Could have had stuff from exhaust port pop into cylinder maybe

You did not see anything out of ordinary with the #2 piston?
Do you have a pic of #2?

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

The only cylinder that had bad compression was cylinder #2 ... Here is a photo of piston #2.

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

If you pull it apart you will most likely find aluminum smeared across the rings near the exhaust port. You have provided a cautionary tale regarding maintainance, I clean the carbs and inspect the reeds each winter, only takes a couple hours. Let us know what you end up doing with it.

Now that the exhaust cover is off I can see all piston rings as they pass by the scavenge ports ... Engine rolls over super easy BTW. The rings appear to be well broken in but there is nothing happening there that I would call catastrophic ... Nothing smeared along the length of the piston ... Any piston. I wonder if I had a head gasket let go around #2 ... Obviously doesn't account for the metal bits ... But ... Fishing in the dark lol.

 

[mphelle8vld]

Re: Suzuki DT55 limp mode? Low RPM's

Some of that shrapnel could have caused damage to the intake side of the piston, are all of the reeds intact?

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

From left to right are the reeds for the top to bottom cylinders. There is no obvious damage that I can see. Looks like some adjustment is required on the top set.

 

[mphelle8vld]

Re: Suzuki DT55 limp mode? Low RPM's

Nice job with the pics. Not many other ideas for the metal debris unless a bearing seal came apart and was shredded by the crank. Are you planning to split the crankcase?

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

Yes I am planning to split the crankcase. Thank you for the photo compliment, I always try to provide good quality cropped pics so you guys get everything you need to help me.

Interesting discovery ..... Check out this picture, there was no thermostat when I opened the t-stat housing!! I wonder how this would have played into my failure ... If at all. Would cause engine to run cold all the time, correct?

 

[mphelle8vld]

Re: Suzuki DT55 limp mode? Low RPM's

Some people remove the t-stat to try and resolve an overheat problem but it's a mistake, it needs to be there to keep water flowing to the entire block. I don't think it caused a problem with the middle cylinder. The gasket surface on number 2 did not show any sighs of blow-by, does the mating surface of the head look OK also?

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

Here is a photo of the head and head gasket mating surface around the #2 cylinder. I don't see any blow-by here either.

 

[mphelle8vld]

Re: Suzuki DT55 limp mode? Low RPM's

Not much else but the rings stuck in their groove by some piston damage to account for the low compression. It will be interesting to see the photos and find out the identity of the mystery schrapnel.

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

My initial plan for the night was to get the crank case split. I started by pulling the oil pump and fuel pump. I then moved onto the flywheel. I used a torque breaker from my VW overhauling days and was able to remove the flywheel nut and washer. I am now unable to remove the flywheel from the crankshaft without a puller. I think my father has one kicking around in his garage, so until tomorrow ...

I spent the rest of the evening putting small parts in zip lock bags and cleaning up. Hopefully this thing is worth rebuilding or else I just cleaned the lower engine cover (tray) for nothing haha.

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

Well I got some pullers. Wow that flywheel was on there good, it needed a couple sledge wallops on the puller tension bolt to free it up.

Once I pried the two halves apart the crank and power packs came out easily.

The low compression in number two is due to the rings being pinned in their grooves.

Also there is similar damage to the top piston but the rings still move freely.

I still haven't found any obvious damage which would account for the metal pieces in crank case #2, unless the missing metal from the pistons mashed together somehow to form larger pieces. I'll have to take a closer look tonight when I take apart the pistons.

 

[mphelle8vld]

Re: Suzuki DT55 limp mode? Low RPM's

The mystery continues... are any of the pieces attracted to a magnet? Did you have the airbox cover mounted? Do you have chunks of piston missing or just what we see in the photos?

 

[Big_worm81]

Re: Suzuki DT55 limp mode? Low RPM's

All of the pieces of debris are attracted to a magnet.

By air box cover do you mean the plastic cover that covers the inlets to the carbs, mine is plastic and the manual refers to it as a silencer cover? If so then yes it was mounted. Are you thinking maybe the engine sucked something metal in through one of the carbs?

There does not appear to be any chunks missing from any piston,unless it came from the wrist pin? I really thought I would find something more with the piston skirts. Here are pistons 1,2 and 3.

 

[mphelle8vld]

Re: Suzuki DT55 limp mode? Low RPM's

That would eliminate aluminum or stainless steel. If you don't find anything obvious it almost seems like something could have been sucked into the intake while bouncing around on the waves, something laying in the pan like one of those metal straps they use to retain wiring.