Engine In Bits, Advice Needed

[szrdave]

I'm currently in the process of rebuilding my SZR660, and have the engine out and in bits. I need to make sure I fix the right bits before putting it back together!

History:

Bike bought with 5k on the clock, now on 15k. Cut out a few times riding through central London on the way home, found out afterwards this was due to the fan and temp gauge not working and it was overheating

This fixed the bike ran fine, and was used mainly for a mixture of commuting short distances and track days (5 or 6) for the remaining 10k. It always used a bit of oil (1L per 1k miles) but this went up a lot just before it died.

The final ride:

Brands Hatch Indy circuit in June. Oil was topped up before I left, at lunch time even adding the 250ml I had brought along didn't get it back to the lower mark on the stick. No joy was had finding bike oil, and I didn't want to stick car oil in, so back on track we went.

All was fine until the end of the last session, when trying to pull up the hill towards druids the engine cut out. It would restart once cool but would die if put under any load.

This is what I found when I pulled the engine apart:

Head - Heavy carbon deposits on combustion chamber roof and valves

Piston - Heavy carbon deposits on crown, some light scuffing to skirt on exhaust side

Gudgeon pin - Witness marks to surface

Con rod little end - Marking to bush

This is the first time I've taken a piston out of an engine, so I'm not really sure how much wear is to be expected on each component. I really expected the cause of engine failure to be obvious, like a cracked piston or loads of scoring to the barrel.

So any advice on the above would be appreciated, especially on the condition of the little end and what may have caused the high oil consumption in the first place. I will definitely be over-boring the cylinder and fitting a 102mm piston, I hadn't originally planned on replacing the rod.

[porter_jamie]

What does the bore look like?

[porter_jamie]

Also, take the valves out, and see how much they float in the guides.

Edit due to being unable to operate shitty phone

[szrdave]

What does the bore look like?

Here is a photo of the bore:

It's quite hard to see, but there is a slight 'polished' section about half way down. Other than that it's fine, no scoring, discolouration etc

[spacemonkey]

Shame you took it to bits. A leak down test ought to have been done before you took it apart.

As Porter said, look at the play in the valve guides/stems. If there's tons of play there the things wouldn't seal properly and the valve stem oil seals would not survive long. Look at the sealing surfaces on the valves and seats too. Then measure the bore in several places to get an idea of if it has worn oval/tapered.

The pin/bush damage is probably more to do with the thing running low/out of oil than the original problem I would think.

[szrdave]

Ok, so as far as 'things to do' go:

• Replace piston + pin
• Bore out cylinder
• Remove valves and check valves/seats (need to buy spring compressor first)
• Replace valve guides

The rod is one piece, is there any way of repairing the little end in-situ?

[spacemonkey]

Ok, so as far as 'things to do' go:

• Replace piston + pin
• Bore out cylinder
• Remove valves and check valves/seats (need to buy spring compressor first)
• Replace valve guides

The rod is one piece, is there any way of repairing the little end in-situ?

I would suggest not going there with the rod. You might be able to bodgineer it but what's the condition of the big end? You might get away with it if it's a roller big end but it might be on borrowed time and while you've got the motor out......

[spacemonkey]

Ok, so as far as 'things to do' go:

• Replace piston + pin
• Bore out cylinder
• Remove valves and check valves/seats (need to buy spring compressor first)
• Replace valve guides

The rod is one piece, is there any way of repairing the little end in-situ?

Also, you won't need a spring compressor to get the valves out. You need something like a socket or a rag under the valve head, a socket or a piece of tube to press strike with a mallet and the collets generally just fall out. If you don't fancy the idea then you can cut a window in the tube so that you can pick the collets out while you lean on the thing to compress the spring.

You'll want the compressor to put it back together mind.

[kja.busa]

Theres some valve spring compressor tools on ebay for not much money, ideal for the home mechanic......

http://www.ebay.co.uk/itm/10PC-CAR-MOTORCYCLE-VALVE-SPRING-COMPRESSOR-TOOL-SET-/230673491182?pt=UK_Hand_Tools_Equipment&hash=item35b53624ee

Regarding the piston a Wiseco or JE item might be cheaper than an oem item. The conrod could be resized/bushed by S.E.P at Kegworth too.

[porter_jamie]

i would give slipstream a call to see how much to put a new rod in, a 102mm piston, and a rebore. prepare for expense. you need to know how much though. i cant remember if 102 will go in the standard liner. probably. everyone used to run 105mm JE pistons in supermono. the old style forging used to crack, so need to change the piston halfway though the season. the new style ones seem to be ok.

do omega make pistons for the xtz? they are the best in my experience.

i would be putting a new rod in. whatever you do you have to split the crank to get the rod out, so you may as well stick a new one in. find out how much a genuine yamaha rod kit is. DO NOT use (unbranded) pattern parts. i had a crank done by sep once and they used pattern bits and it didnt last very long. the yamaha bits seem to last forever.

the other option is a carillo. shiny

[szrdave]

You might be able to bodgineer it but what's the condition of the big end?

I've got no intention* of bodging anything, I'm happy to take the time (and spend the money ) to get everything right. But on the other hand I want to avoid turning it into an epic that never gets finished.

Advice taken though, I'll price up the tools needed to get the crank out and the cost of having it rebuilt. It may end up being more economical to source another engine. One went on ebay recently for £400 that had just had a refresh with big bore, light head work, new rod and a paint, I should have had a bid!

Regarding the piston a Wiseco or JE item might be cheaper than an oem item. The conrod could be resized/bushed by S.E.P at Kegworth too.

The plan was to go for an aftermarket piston with a slightly higher compression ratio, stock is only 9.2:1 as it's a off road plodder.

I have a gudgeon pin here from a ford Ka (the piston is fucked, i have that too lol) and the centre part is smooth with almost no wear in comparison to yours (i can take a pic and post it if you want to see)

No need for a pic, I think it's obvious mine is fucked. Thanks anyway though!

*well, as much as possible anyway

[szrdave]

i would give slipstream a call to see how much to put a new rod in, a 102mm piston, and a rebore. prepare for expense.

I did consider giving them a call, but I'm guessing it would be more than the value of the bike!

I was hoping it would be a case of a new piston and a re-bore and job done. With the couple of snapped bolts that need extracting, exhaust headers still stuck in exhaust ports, new valves/seals and a crank rebuild I think I'll just keep an eye out on ebay/gumtree etc for a replacement engine.

SZR =

[szrdave]

Just emailed slipstream to ask for a rough idea of price to sort the bottom end out and bore out the cylinder.

Anyone care to take a guess?

[porter_jamie]

get the prices from yamaha tomorrow for a new rod, and a standard piston, looks like the bore will go again. you need to know how much these are from a dealer, then you know if slipstream are taking the piss.

guess - rod 150 quid, fitting 45, piston 150

also, new cam chain, tensioner, new seals all round including the valve seals, and gaskets, new clutch basket nut and washer, new ignition nut and washer

get the bottom end apart, you need to check the oil pump

[szrdave]

No reply from Slipstream yet, but now I've got over the initial shock of having even more to do to get the bike back on the road I've decided I might as well do it myself.

There is a machine shop at work and I used to work for a bike dealership, so that'll help. Anything else like rebuilding the crank and boring out the cylinder will probably go to Slipstream unless there are any recommendations for other places down south?

And obviously there'll be plenty more questions here as I get stuck!

[Phil Norton]

Have you seen what Kayla has just put up for sale? Know where my money would be going, less stress too.

[theo]

Also, you won't need a spring compressor to get the valves out. You need something like a socket or a rag under the valve head, a socket or a piece of tube to press strike with a mallet and the collets generally just fall out. If you don't fancy the idea then you can cut a window in the tube so that you can pick the collets out while you lean on the thing to compress the spring.

You'll want the compressor to put it back together mind.

Dont do this. Never, ever do this. I believe this may be an extract from Tractor Davidson's 'Successfully rebuilding a Hog' manual.

Buy a valve spring compressor

[Mr.Pigdog]

G'day mate-I second the buy a spring compressor crew(laser do some fine bike specific tools these days)I got a number for an old boy lots of dealerships use for the denotes and pistons-he's over fleet way,pm me if interested and I'll pass his number on

[Mr.Pigdog]

Seems I also belong to the doublepost crew?

[porter_jamie]

kayla is flogging a complete motor, job done

[Kayla]

Have you seen what Kayla has just put up for sale? Know where my money would be going, less stress too.

I PMed Dave about my engine before I put it up in the for sale bit

[szrdave]

This would obviously be the sensible and simple solution, bolt the engine back in and job done. However, I've wanted a bit more 'go' from the SZR since buying it and now the engine is in bits it's the perfect opportunity for a spot of tuning.

Plus the demise of my engine was largely due to my own stupidity, so I think I owe it a rebuild! I've had a better scan through the owners manual and it looks like a relatively simple engine to work on , although from experience gained so far if Yamaha see the chance to add a shitty little extra fastener that will seize up and be a bastard to remove they've taken it.

[markmac999]

Piston and barrel look fine, They're all like that sir.

New rings and hone the barrel. Bush the small end IF the big end's fine.

Check those valve guides and definitely definitely examine the oil-pump, given the state of the gudgeon pin.

[Thom_1991]

You knowingly ran it low on oil, you're not related to Josh are you?

[szrdave]

You knowingly ran it around a track low on oil, you're not related to Josh are you?

Nope, I'm just a tit

[V6Jon]

You knowingly ran it low on oil, you're not related to GPZRX are you?

Fixed