Sluggish cranking and won't start

[drix]

Hi all

I've got round to fit my spare engine into my black rex whilst I have the original motor refreshed & upgraded however, I'm facing a bit of a problem so thought I'd consult the TRX bible, a.k.a you lot

So the engine I am fitting is an unknown quantity to me (never heard running) and allegedly has an 878 kit.. anyways, engine in the frame, everything connected, press start and all I am getting is a super slow/sluggish cranking and engine won't fire up.

So I've swapped over with my second TRX, the batteries and starter solenoids but still the same story (second TRX starts fine with any parts combo here). I have checked the battery's earth cable and it's connected where it should be. I have a spare starter motor with cable so I'll swap that over tomorrow as a last resort but don't really as it means an engine oil flush

After that, I'm sure where to go next, is there anything I should be considering here?

Cheers guys
Adrien

[Rod.s]

Hi all

I've got round to fit my spare engine into my black rex whilst I have the original motor refreshed & upgraded however, I'm facing a bit of a problem so thought I'd consult the TRX bible, a.k.a you lot

So the engine I am fitting is an unknown quantity to me (never heard running) and allegedly has an 878 kit.. anyways, engine in the frame, everything connected, press start and all I am getting is a super slow/sluggish cranking and engine won't fire up.

So I've swapped over with my second TRX, the batteries and starter solenoids but still the same story (second TRX starts fine with any parts combo here). I have checked the battery's earth cable and it's connected where it should be. I have a spare starter motor with cable so I'll swap that over tomorrow as a last resort but don't really as it means an engine oil flush

After that, I'm sure where to go next, is there anything I should be considering here?

Cheers guys
Adrien

How long has the engine sat? Are the rings free? Is there spark at the plugs?

I'd remove the plugs, pour some thin oil down the bores and turn it over, it may just be gummed up with crud, another thought is has the engine sat with the cylinders facing down? There may be engine oil in the chamber…lots to think about

[cobbadiggabuddyblooo]

Yep go through the motions..
Pull the plugs out and turn it over by hand to get a feel of things to start.
If it's been sitting a while there will condensation built up and moisture in the oil.

Got a spare hour up your sleeve...
Much easier to do with the motor out of the frame as you can rotate the motor get oil from the gearbox and head out. Found that out when I went to paint the motor .
Cleaned it thoroughly and wanted to paint the base first and turned the motor on it's head. While getting things ready I came back and found a pool of oil on the floor and had to clean the motor again as well as the plastic drop sheet..

[drix]

Thanks for the pointers guys

The engine's been sat for around 3 years. I've cleaned it up and painted it three weeks ago so it's been tilted in all ways possible so most of the old oil should've been flushed out (I had a similar experience to you Cobba with oil dripping out whilst getting ready for paint! ).

I took the plugs out today, swapped starter motors and moved the battery earth from engine casing to frame and still the same sluggish cranking. Funny enough though, no spark at the plugs and after a total of circa 90 seconds of cranking, the battery gave up (I charged it last night and is now on the charger again - battery is an 18 months old Yuasa YTBX12). It feels like the battery/starter motor are having a hard time (the starter motor cable getting quite warm) and the no spark makes think of an electric issue more than the spare motor having a shot crank or else (just my impression). Funny thing is that the bike was running fine on its original motor two weeks so I must've done something wrong somewhere if it's electric , where is the million dollar question!

[cobbadiggabuddyblooo]

While the plugs are out remove the centre Bung on the alternator case and turn over the motor by placing a socket onto the bolt holding the rotor to the crank. If it still feels like a lot of resistance, remove the starter and this will eliminate the starter gear. If still feels like too much resistance. Remove the cam cover, remove the cams and hope for the best.

[drix]

While the plugs are out remove the centre Bung on the alternator case and turn over the motor by placing a socket onto the bolt holding the rotor to the crank. If it still feels like a lot of resistance, remove the starter and this will eliminate the starter gear. If still feels like too much resistance. Remove the cam cover, remove the cams and hope for the best.

A bit more investigation this evening and it turns out the cams were over tightened or sticking (or both). I've loosened them and the engine cranks over fine with sparks back at the plugs. Now I need to inspect the state of the cams and see what's too damaged/needs replacing following this. Lucky I decided to keep the spare cam set I was selling on here not so long ago!

Thanks Cobba for the pointers, mechanics is a hobby more than anything so it's a constant learning curve for me & the bike here

[cobbadiggabuddyblooo]

Play it safe mate and take off the oil pump case. Good chance you'll be able to reuse the gasket.
Check the teeth on the crank that the cam chain runs on.
Check valve clearances as a reference and jot down on a mud map.
Bit of luck you may be able to polish up where the cams sit on the head and the caps with wet n dry and wrapped around something like a broom handle.

Just remember after getting crank in the right position , the inlet cam will be loaded as it's slightly pressing on the inlet valves on no.2.
Remove...
Tensioner Spring and the Cam chain tensioner
Front cam chain runner
Exhaust cam
Place the runner across the head between the cams so the chain doesn't accidentally fall down the cam chain galley.
Unload the inlet cam and remove.

Assembley start with you exhaust cam first
Place in position with cam chain and torque down.
Put the runner back in..
Place the inlet cam in place and torque down and before you rotate it jossle the cam chain around the cam sprocket retaining nuts and hold your tongue right... Lol
Once inlet & exhaust cams are in position via marks on the cam sprocket, slip the chain around the sprocket and place the tension back in place.
You'll find most times the inlet cam will stay in the correct position even when loaded but just don't bump anything..

Handy hint...
Mark the top of the cam chain tensioner before you remove it so you don't put it back in upside down..
Before refitting..
Count how many clicks the tensioner pushes back in so when it comes time to refit, once bolted in place you can put a small Allen key into where the tensioner Spring fits and count how many clicks it takes to load itself hard against the cam chain. ( around 9 clicks )

While cams are out..
Look at each shim and note the valve position and size which should be stamped on them and jot down on your mud map with earlier clearances.
Once all back together, check clearances again and if you need to change any , you'll know what size you need..

[drix]

Thanks Cobba but all that feels a little out of my comfort zone but one day I'll get round to that sort of work myself! Will prob give my first shots on bikes that I'm less "close to" than I am to the TRX

I've farmed the work out to what seems a reputable place that is within a convenient 10miles from home.

[cobbadiggabuddyblooo]

Hope all goes well mate, I'd suggest asking them just to whip the oil pump cover off tho, just to check the crank sprocket where the cam chain runs as it would be a shame to have them do the work to the head and forking out money only to find the crank needs replacing.

[drix]

So the cylinder head on the spare engine has had it by the looks of it

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So my original engine has had a good clean, a respray and is now back in it's frame whilst I crack the spare engine open for inspection..



And maybe fit a few goodies for an initial test



Time to have fun and work/learn/practice on engine internals

[cobbadiggabuddyblooo]

Good one, a toy to practice on and familiarise yourself with things..
You'll have plenty of spares for your original motor now ..
Engine cases, water pump and alike... Keep ahold of the 90* waterpipe that bolts to the top of the head as they are no longer in stock, and if not looked after suffer corrosion ... Grease it up and stash it safely away for that rainy day...
Bit of luck the crank will be good so another rainy day item to keep..
Look on the beginning of my rebuild thread and is explains how you work out the main and big end bearing shell size(colour) . Draw a crank and note them down to match and tuck it away in with your downloaded workshop manual...
Watch out for that dreaded bolt that snaps on the top sump too...

Enjoy

[drix]

Good one, a toy to practice on and familiarise yourself with things..
You'll have plenty of spares for your original motor now ..
Engine cases, water pump and alike... Keep ahold of the 90* waterpipe that bolts to the top of the head as they are no longer in stock, and if not looked after suffer corrosion ... Grease it up and stash it safely away for that rainy day...
Bit of luck the crank will be good so another rainy day item to keep..
Look on the beginning of my rebuild thread and is explains how you work out the main and big end bearing shell size(colour) . Draw a crank and note them down to match and tuck it away in with your downloaded workshop manual...
Watch out for that dreaded bolt that snaps on the top sump too...

Enjoy

I got two of those 90degree water pipes stashed on a shelf already Cobba and yes, this engine will be a bank of spares should anything happen to my original lump. Will certainly read through your thread Cobba!

The idea for this spare engine (for now) is to rebuild it and fit a set of tdm900 barrels/pistons/rods which I’ve had for a while now. I’m hoping to be able to swap the 850 rods over with the 900 ones by removing the lower sump. But I guess whilst I am at it, I could just split the cases open and have it all checked.. what’s the general consensus here on the options?

If that goes well and the engine is viable, I have some 2mm valves and thinking of getting some cams to compliment.. fun times ahead anyways and probably quite a few hours tinkering in the garage over this!

[cobbadiggabuddyblooo]

I think you'll find you'll need to machine out the top case for the larger 900 barrells to slot down in.
Grab the 900 barrels and see if they will fit while you have the 850 barrels off...
You'll probably need to rebalance the crank with the 900 rods been 22% lighter and plastiguage the big end clearance of both the 850 and 900 rods to get the correct size shells...
Any chance you can post up the 3 weighs of the 900 piston , 900 pin and the Rings????
Handy info to have...