bottom end problem please help!

[bikerboi1946]

Hi all,

new here 1st post, was given a zxr400 1990 H model, was told the engine had started making a very bad noise, this was 5yrs ago as the owner left it in the shed till now! anyways got it running and sure enough very noisy, check cam chain etc all good valves all good so had to pull head then barrels then check the pistons...ah ha, no4 conrod is slapping up and down good few mm either way compared to none on all other 3. So I found the problem.

now for the cure?!

what's the next thing I have to do?, never stripped a 4stroke before so I am learning but it seems easy enough

I am going to have to split the cases to get the rod off as far as I can see and that doesn't seem too hard, once its all apart can I just replace a part or will crank need grinding etc?

cheers.

[bikerboi1946]

how come 16 people can look at the post and not 1 person replies?

surely someone must have rebuilt the bottom end before and knows if it would simply be shells or if its more than that, anybody?

[jake]

erm.. i dunno
i have had that problem before on a race engine last year, and i just gave my engine to my builder and he sighed and said words like boloxed and peice of shiet.
this probs does'nt help im sorry

[cargo]

how come 16 people can look at the post and not 1 person replies?

surely someone must have rebuilt the bottom end before and knows if it would simply be shells or if its more than that, anybody?

"can I just replace a part"



Yes there are shell bearings
and yes if they are knackered they can be replaced
and yes if your crank is damaged it can be repaired
and yes if you conrod is knackered it can be replaced

Shock news.......................

every single part of every single ZXR400 ever built can be replace with a new part

BTW I've rebuilt more bottom ends than I can be bothered to remember from 1970s Z650s to 2002 GSXR done em all..................


Now go take it apart inspect the damage and replace the bits that need replacing easy really

[bikerboi1946]

well you sound like the man with the answers then!

what causes it to wear out and go loose?

and as long as its not literally falling off which it isn't , is it simply just a case of two shells and put it back together again?

when I take it apart and split the rod as long as the crank is not scored/worn on No4 will this mean its ok to go ahead with just the shells?

excuses all the questions and my ignorance, just I have never had an engine apart down to the crank before so not entirely sure what to do?

[cargo]

Hard to tell from here what has caused it..................I'd guess that there has been some kind of oil failure

Could just be good old fashioned high milage..............anyway get it apart and inspect the damage if your lucky a new set of shells will fix it.

You'll need to check all the bearings and you will need to figure out what actually happened and fix that too

However it could just be cheaper to replace the engine if the crank is worn damaged always loads on ebay...................... any ZXR400 engine will fit

[will#224]

Take out a micrometer, a set of verniers and perhaps some plastigauge to measure and check if everything is within tolerances or at least comparable to the other cylinders/rods. If you dont have those tools then i expect you'll manage to get it back together and somewhere down the line the same will happen again.

[bikerboi1946]

i'm thinking 2nd hand engine then sell of the good parts from this one like head etc.

you say any engine will fit my H model? I thought they changed the carbs and a few other bits over the years?
plus the water pipes on the back of the engine, on the later engines, the top one points east opposed to my H model pointing west, will it matter or can i turn it around?

[RedexRobB]

you can turn it round

[bikerboi1946]

ha, sweet!

so it is different and a known thing on the later engine then? thought I was imagining it!