1992 350D Starting problems

[TRX Student 151]

So, you've got spark and fuel/starter, but no compression(air) you've for sure determine that it is out of time? And then tested compression , with low results? Can one get a good compression reading on a motor that is out of time? Have you checked your valve clearances at top dead center? That is where I would go next, if I were working on it. Get a feeler gauge and check valves. I've seen some get stuck open before, thereby eliminating compression.

[retro 4,048]

2 hours ago, TrxPipUK said:

Ah I think I see where I've gone wrong lol... my carb isn't on the bike. So the carb needs to be on to hold pressure in the cylinder? 

What does the oil do? Does it create a seal between the piston and the cylinder? 

 

Thats OK, the carb doesn't need to be on it.

 

Adding a small amount of motor oil to the cylinder helps to seal worn out piston rings and worn/scored cylinder, so if you notice that the compression pressure increases by 10-15% or more during a "wet compression test" that indicates bad rings and a worn or scored cylinder wall.

 

At this point (with only 50 PSI compression) I'd check the valves lash and make sure that each valve is completely closing. Make sure none are sticking open or bent. Then check the cam timing after removing the Rocker box cover from the top of the head. Let us know if you decide to yank that cover... there are three or four of those bolts that are prone to snapping off when attempting to loosen them.

[retro 4,048]

I should add... you've already discovered that the cam chain is worn so badly that the chain tensioner is almost fully extended. You'll have to replace that chain for sure... got no other choice. The diagnostic steps you are now performing are motor teardown steps. These steps are for discovery of any additional problems. But you are tearing this motor down right now... go ahead and tear it down step by step and learn what you can without spending any money on testing tools.

[shadetree 5,864]

23 hours ago, TrxPipUK said:

Ah I think I see where I've gone wrong lol... my carb isn't on the bike. So the carb needs to be on to hold pressure in the cylinder? 

What does the oil do? Does it create a seal between the piston and the cylinder? 

 

carb does not need to be on engine to do a compression test !!!.

[shadetree 5,864]

as retro said ^^^^..throttle held wide open, crank it over for a few secs, compression should climb as your cranking it over, if all you got was 50 psi ?, your not looking good engine wise. time to check the adjustment on valves , and pray you did not bend or break a valve from the cam chain stretched too much ?, and hitting the piston. as I told you pages ago, the cam chain was stretched by looking at your cam chain adjuster, THIS IS A MUST REPLACE PART !!!, if you crank it over as is ?, all your doing is applying damage to what you already have going on !.

[TrxPipUK 169]

Awesome.. Thanks for all the help peeps. I have a new cam chain so the next step will be removing the rocker cover box, check the timing properly, check the valves and probably try to get a look at the piston and cylinder. 

 

Thanks everyone 

[F250 guy 107]

1 hour ago, TrxPipUK said:

Awesome.. Thanks for all the help peeps. I have a new cam chain so the next step will be removing the rocker cover box, check the timing properly, check the valves and probably try to get a look at the piston and cylinder. 

 

Thanks everyone 

I was gonna say that but I didn't know for sure on your model so I chose to keep quiet lol

[Fishfiles 20,145]

another thing to look for after you take it apart , which I think at this point looks  inevitable -------  if your chain is worn out bad and has been run that way for a while  , chances are real good that your chain guides are going to be worn out and damaged ---- I seen a loose  chain chip and eat the rubber coating off the guides and clog up the screen in the bottom of the case with little pieces ---- 

 

I wouldn't buy any parts till you make a full assesment of what all is going on , low compression could be from a bad connecting rod , letting the piston wobble in the jug and egg shaping the bore , if you replace the piston and bore the jug and don't fix the rod , it won't last long at all and do it again 

 

You don't need the carb on to compression test it , I was just telling you to hold the throttle wide open while doing a compression test cause if the carb is on them it can make a difference 

[TrxPipUK 169]

3 hours ago, Fishfiles said:

another thing to look for after you take it apart , which I think at this point looks  inevitable -------  if your chain is worn out bad and has been run that way for a while  , chances are real good that your chain guides are going to be worn out and damaged ---- I seen a loose  chain chip and eat the rubber coating off the guides and clog up the screen in the bottom of the case with little pieces ---- 

 

I wouldn't buy any parts till you make a full assesment of what all is going on , low compression could be from a bad connecting rod , letting the piston wobble in the jug and egg shaping the bore , if you replace the piston and bore the jug and don't fix the rod , it won't last long at all and do it again 

 

You don't need the carb on to compression test it , I was just telling you to hold the throttle wide open while doing a compression test cause if the carb is on them it can make a difference 

Thanks man for the information, extremely helpful and appreciated. All this is gonna be a real big learning step in mechanics for me haha. Looking forward to it though 😁

[TrxPipUK 169]

UPDATE:

Today I started looking into the engine and taking her apart. I checked the timing and to me it looked pretty good. The chain seemed to be a decent tension and not slack, but the tensioner was fully extended. I'll replace it anyway I reckon. 

After that, I removed the rocker box and looked at the underside of the valves (still need to get a valve spring compressor) and the top of the piston. Wondering if it's worth taking off the cylinder and seeing what state it's in considering there was such low compression? Also replacing the rings and maybe the piston? 

 

Would be great to hear your thoughts, thanks 🙂

[toodeep 1,758]

It looks like it might have had a condensation/moisture issue while in storage. I would probably do the piston/rings while your there and if the cylinder looks bad plan on getting it bored.

[retro 4,048]

How do the cam journals, rocker arms and cam lobes look? Is there a hole in the left side header pipe near the flange, or is that just junk burnt onto the pipe?

[TrxPipUK 169]

2 hours ago, toodeep said:

It looks like it might have had a condensation/moisture issue while in storage. I would probably do the piston/rings while your there and if the cylinder looks bad plan on getting it bored.

Yeah it definitely looks that way. New rings and possibly a bore are on the cards.

[TrxPipUK 169]

1 hour ago, retro said:

How do the cam journals, rocker arms and cam lobes look? Is there a hole in the left side header pipe near the flange, or is that just junk burnt onto the pipe?

I'll get some measurements and pictures of those and report back. But to my eye everything looks to be in good shape with them.

The left side header pipe had a huge crack in and has been brazed back up. No holes. 🙂

[shadetree 5,864]

this far in, it would be smart to pull the cylinder, have it bored over if out of spec's ?. new namura piston kit, check the rod !!!, new top end gasket kit. cam chain looks stretched a tad, i can see that the timing marks are not quite lined up with the top edge of cylinder in your pics ^^. deff pull the valves, check for bent valves ?, clean them up if they are good ?. all said and done, i think your doing great digging in !!!.

[TrxPipUK 169]

1 hour ago, shadetree said:

this far in, it would be smart to pull the cylinder, have it bored over if out of spec's ?. new namura piston kit, check the rod !!!, new top end gasket kit. cam chain looks stretched a tad, i can see that the timing marks are not quite lined up with the top edge of cylinder in your pics ^^. deff pull the valves, check for bent valves ?, clean them up if they are good ?. all said and done, i think your doing great digging in !!!.

Yeah I was thinking along these lines. I'll pull the cylinder and check how things look there then decide on a bore and new piston kit. 

I'll get the cam chain changed out as well. I can see what you mean the marks aren't quite lined up. 

I'll get the valves out once I have a spring compressor.

Thanks shade. I'm quite enjoying it actually lol... Good to learn about these things 🙂

[shadetree 5,864]

this is not a trx350D ?, but it does show you how the timing marks should line up !.

[TrxPipUK 169]

8 hours ago, shadetree said:

this is not a trx350D ?, but it does show you how the timing marks should line up !.

Ah okay. So the Mark's should be perfect really. How do you go about adjusting the timing? Is it just a case of taking the chain off, lining all the marks up then putting the chain back on?

[retro 4,048]

Those marks may never be perfectly lined up even with a new chain installed. Yours is still in time so the cylinder and right side cover, clutches and oil pump need to be taken off next so you can replace that chain. Once you begin to lift the cylinder up stop and hold the jug with one hand while you stuff a clean rag down around the rod into the top of the crankcase with your other hand, to prevent falling dirt and possible broken piston rings or a loose circlip from falling into the case. Then lift the cylinder the rest of the way until the piston is out. Leave the rag in there until you're reassembling. Lets see some pics of those rocker arms and cam journals eh?

[shadetree 5,864]

7 hours ago, TrxPipUK said:

Ah okay. So the Mark's should be perfect really. How do you go about adjusting the timing? Is it just a case of taking the chain off, lining all the marks up then putting the chain back on?

pretty much. as retro said ^^..if there is worn crank teeth ?, then chances are your timing marks may never line up 100% ?, but most times, all mine have been dead on.

[TrxPipUK 169]

On 2/18/2020 at 11:28 AM, retro said:

Those marks may never be perfectly lined up even with a new chain installed. Yours is still in time so the cylinder and right side cover, clutches and oil pump need to be taken off next so you can replace that chain. Once you begin to lift the cylinder up stop and hold the jug with one hand while you stuff a clean rag down around the rod into the top of the crankcase with your other hand, to prevent falling dirt and possible broken piston rings or a loose circlip from falling into the case. Then lift the cylinder the rest of the way until the piston is out. Leave the rag in there until you're reassembling. Lets see some pics of those rocker arms and cam journals eh?

Great thanks for that advice on removing the cylinder. To inspect the rocker arms do I need to remove them from the rocker box cover?

[shadetree 5,864]

1 hour ago, TrxPipUK said:

Great thanks for that advice on removing the cylinder. To inspect the rocker arms do I need to remove them from the rocker box cover?

no you do not, you just need to inspect the rocker faces is all, and the tappets on them, no need to pull them out, unless your replacing the O-rings on the shafts ?.

[TrxPipUK 169]

2 hours ago, shadetree said:

no you do not, you just need to inspect the rocker faces is all, and the tappets on them, no need to pull them out, unless your replacing the O-rings on the shafts ?.

Okay that's good to hear lol. Not planning on replacing the O-rings no. I'll get some pics later on once I've finished some jobs on the farm.

Thanks shade

[toodeep 1,758]

If the o-rings come with the gasket kit I would replace them. 28 year old o-rings are going to be hard as a rock and you don't want them to start leaking a month after you get it going. Just something to think about since it's easier to do it now vs later.

[TrxPipUK 169]

Right, so I wasn't sure what angles ect to take the pics, but here they are. Gonna take some  measurements at some point as shown in the manual. Let me know what you think 🙂