Bottom end rebuild (AR)

[gregorious77]

So I noticed my bike was sounding a little rattly (ticking noise) but not really bad as these engines are pretty noisy anyway. It sounded different anyway which worried me.
I changed the gearing recently too which made it taller. Heading out one cold morning I thought I would test the taller gearing on the motorway but as I accelerated she bogged and slowed down. I initially put this down to possible carb icing as it was around -2 - 0 degrees. I pulled off the motorway after tickling it along out of the bogging zone and it died at a set of lights.
Long story short I done an hour or so green laning and headed home to do a compression test while it was still warm.

125 psi is low so took pipe off and fingered her port.
Piston was a bit flappy so pulled top end.
https://drive.google.com/file/d/0B0fBOH ... sp=sharing
Bore had a step the size of the san andreas fault and flywheel had some up and down play.
https://drive.google.com/file/d/0B0fBOH ... sp=sharing

So I split the cases at the weekend and today pressed the crank out. There was a lot of oily black shite behind the main crank bearing (geni side) and up the small hole to the top of the transfer port. It looks like maybe shite has got in through the crank seal although the seal was in good shape. Either that or shite got in through the exhaust a few weeks back when I rode through a deep (to bottom of tank) muddy rutt.
Any ideas on this? looks like combustion carbon which is why I am in 2 minds how it got in there.

[gregorious77]

[gregorious77]

Big end seems fine. There is no radial play only side to side.
I have new mains plus associated bearings and crank seals on the way so should be all rebuilt soon.
I am going to seal the exhaust better and keep away from deep muddy water even though it is fun to ride through it.

[fallenmikethebike]

Have disconnected the carb warming circuit?
Gritty puddle rut water would play havoc if it got in around the mains bearings, and would certainly exacerbate any existing wear.
Mike

[gregorious77]

carb warming still present and correct. The bore only had a few hours on it so I am sure it was muddy water in engine. Just not sure on its route of entry. After the rutt I had missfiring and a lot of steam out of the exhaust but airbox was dry as a bone. I am thinking it may have flooded the exhaust through the slip on connection between stinger and silencer (DEP pipe) then got sucked in exhaust port maybe.

[gregorious77]

Received the mains and they are in the freezer ready for install. LT a tad pricey (£30.95 + VAT ea) at over double the price of bike-parts-honda.com (£14.99 + VAT ea). Reason for LT purchase though is they had them in stock whereas BPH would have had to order them.
Just waiting on gaskets and seals plus the clutch arm needle rollers (and blind puller) to make a start.

[knackeredMk1]

Some serious crud got in the bottom end. Either the engine got flooded through water or more likely the Gen side crank seal had gone and as the gen cover does not seal it can easily suck in whatever grit gets in.

I would suggest you get the bore replated as that is showing ware. You could take the bore out to a more conventional size at the same time so you could use a TRX piston for replacement in future and gain a bit of capacity while you are at it.

[fallenmikethebike]

There are some RTV,S [ room temperature vulcanising silicones ? ] that can withstand 2T exhaust tempertures and will give a flexible sealing joint. Are you going to warm the cases [ gently ]in the oven as well? Or apply heat locally when putting back together?
Were the bearings in the balance shaft all good? Easier to do them at the current stage of strip down.
Mike

[gregorious77]

Knackered, I have a spare good barrel still on its original bore and a decent like new piston. I have purchased new rings and this top end will be going on. The one that was on there is toast for sure.
I am still not 100% sure how all the poo got in the bottom end but like you say the geni side was full of mud also so could have got past the crank seal but I didn't have any lean symptoms in normal riding so not sure. I did drown the bike and after that crossing there was a misfire and tons of steam out of the exhaust. Noised started shortly after his incident as the next ride was the one with bogging and ticking.

Mike, I have already done the balance shaft previously so that is all good. I will be putting the cases in the oven at 100 - 150 ish most likely to give a nice even warming up.

[gregorious77]

This was the point of damage I believe.

[fallenmikethebike]

Is the vid of three ended lane in Hampshire?
Almost certainly the muddy water is the culprit, is / or was the little drain off hole clear on the gen side cover? They tend to get blocked easily? As KNMK1 says possibly also pulled through the gen side seal, this might be caused by vacuum created in the cases?
The steam would be the drawn water being boiled off from in the pipe et al.

Mike

[gregorious77]

Yup that lane it between Warnford and the A272 West Meon hut. Has 3 rutts. Not sure on drain hole clear or not but whole gen side was very muddy under the cover.

[gregorious77]

So....... who has done a bottom end on a CRM before? book does not go into much detail on the putting back together except that it says dont let the bearings touch the bottom end of the case. This is not too helpful as if they are installed too shallow then I have no chance of pulling them in further without risk of damaging them as I would be pulling by the inner race. It also shows the gen side needs to be firmly home on the crank.



I was going to drop both mains into the case then pull the crank into the right hand case then pull the left case on last. Now I am not sure if this will be correct!?!

[gregorious77]

soooo........
any thoughts peeps?
Normally I would drop the cold bearings into the warm cases then let the whole lot warm up and pull the crank home into the right hand case followed by pulling the left hand case onto the crank. Only problem with this is the book says dont put the bearings all the way down into the case and also shows the geni side bearing must be fully home on the shaft.
Do I put the bearings onto the crank first then pull it into the cases? I dont want to damage the bearings by pulling them in by the inner race if you get my drift but its the only way I can ensure they are not too deep in the case I guess.
1. Cool the crank and warm the bearings, pull them on to the crank.
2. Cool crank/bearings and warm cases then pull into right case to specified height.
3. Pull left hand case onto bearing until cases closed.

Answers on a postcard

[fallenmikethebike]

Option 2 is the only option that won't potentially bugger the new bearings.
Like you, I've done bottom ends previously, but not a CRM.
Mike