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Smokinrider's technical and mechanical tips
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Author:  smokinrider [ Thu Dec 29, 2016 12:41 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips

in the near future I will be asking the mods to tidy this thread up for me, we have all had a chance to read the responses and some I will keep on it, but those that form more of a chat discussion I will ask to be removed.

If a thread gets too long the earlier posts tend to get overlooked.

Don't take it personally or think the forum gestapo have intervened its will be done so as to condense the thread down to a manageable level.

Author:  smokinrider [ Thu Dec 29, 2016 2:28 pm ]
Post subject:  Smokinrider's technical and mechanical tips

In order to shut Joel up as he will no doubt post something about how great they are, a rivet link is as good as and in some ways better than split link.

Author:  Joel [ Fri Dec 30, 2016 9:52 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips

I still think split links are shit though....

Author:  smokinrider [ Mon Jan 16, 2017 1:15 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips

So ive seen several posts recently here and elsewhere asking for possible causes and cures for why a bike either wont start or wont run.

Lets start at the basics.

If your riding along and the bike conks out then it will be one of a two things. A) Something simple or B) something major.
If the bike was not exhibiting any signs of an issue (a splutter, a funny noise, knocking banging etc) then its safe to assume that it will be something minor.

If it was rattling like a can of stones and stopped with a bang, then it might well be something major.

In order to diagnose a fault yourself, all you need to do is follow the same procedure any mechanic would do, if you took it to a shop.

What you DONT do is ask for advise on a forum of facebook page, where all you'll get is 1001 different opinions.
What you also DONT do is start swapping bits and pieces over at random. Not only do you want to fix the bike, you also want to KNOW why it broke down.
Cleaning the carb, swapping the plug, coil, kill switch, ecu etc all at once may fix the problem but you'll never know what the issue was next time it happens!

There are only a few reasons why an engine wont run.
1)Fuel, it either hasn't got any in the tank or the means of getting it into the engine has developed a fault.
2)Spark. It either has a spark or it doesn't.
3)Compression. Again it either has compression or it doesn't.
4)Timing (Valves). They are either timed correctly or they are not.
5)Ignition timing. Again its either right or out.

So....First things first. What happened? If you're riding along and the bike just dies with no unusual noise then the chances are its 1 or 2. Have you been through lots of puddles or deep water? were you flat out on the road when it died or pootling along on a lane on tickover? Don't overlook the obvious and NEVER EVER ASSUME anything (new parts can and do fail). If you broke down 2 mins after you filled it up at a garage, check you didn't put diesel in it!! Or a wire may have simply come apart of shorted out.

If an engine dies while flat out on the road or trail, it will either be, your carb cant keep up with the fuel you're demanding. once left to refill bike should restart and run ok. You've run too hot and lean that you have melted the plug or worse still the valves. You have over revved it and hit the valves on the piston. Remember the rev limiter only works on the way up through the gears. An aggressive down shift can accelerate the piston so quick the valves wont have a chance to return on their springs.

To help understand this ive condenced it down to laymans terms.

At 6000 rpm the piston hits TDC 100 times a second. that means its travelling say the 72mm stroke twice (up and down), 100 times every second at a piston speed of about 50km/h (think ive worked that out right). so it goes up from (BDC) 0 to 50kph back to 0 (over 72mm distance) to TDC then downwards at 50kph 72mm back to zero (BDC), 100 times a second.! How these engines don't destroy themselves more frequently is a testament to the development of metals and oils. The reality is its max piston speed is twice what I have put as you have to accelerate from zero and decelerate back to zero. peak piston speed could be in excess of 100kph. Just take a moment to think of the load every revolution of the engine on the big end, as its throwing the 500g or so of piston up and down! remember also this is 6000rpm. if its a modern 4 stroke this could be up to 12000rpm so the speeds and forces will be a lot lot higher.

On a 4 stroke every revolution will see the inlet or exhaust valves open and close.
soooooo your valves has about 0.01 seconds to open and close (half that at twice the revs). not a lot of room for error especially as they are timed critically for performance. On the BSB engines the piston to valve clearance was set at about, if I remember correctly, 0.1-0.2mm, you had the inlet valves opening while the piston was still on its way up on the exhaust stroke (with the exhaust valves open) so the exiting exhaust gasses would suck the fresh cold charge in. by the time the piston was at TDC the inlets were well on their way to being fully open and a gnats cock away from the piston crown. bear in mind valves will stretch at high revs there is little margin for error. Hence why the most common cause of engine failure in competition engines is a dropped valve, which in turn usually causes a thrown rod as you stop the engine dead at max rpm, (somethings gotta give!) This is one of the reasons you have to replace the titanium valves on your bike at 100-200 hours. Of course as they stretch they become thinner on the stem so will move about in the guide causing wear and friction. (another reason why 2 strokes are better than 4 strokes)

Anyway I digress, unless you've been riding like a cock then this is unlikely to be the reason why your bikes stopped. The most likely cause is a broken wire or water ingress into the electrics or carb.

So first Check you haven't run out of fuel, then check the fuel tap hasn't become blocked. If all's ok there proceed to the carb (if you have one) If you can, undo the drain screw. Is there fuel there? If there is, then this is possibly not the issue. But the jets may be blocked. you can just lean the bike over and see if fuel leaks from the overflow. doing this may also clear a sticky float or dislodge any gunk in the carb.

Next, Check for a spark. Take the spare spark plug you carry in your tool bag and connect it to the lead and rest it on the head of the engine or somewhere where it will get a good earth. Kick or crank the engine. Is there a nice fat blue spark. If so then that's all good. Now remove the spark plug from the engine and replace it with the known good one you've just tested. Look at the one removed from the engine. is it wet? is it sooty? is it white? does it smell of fuel? Wet means you've flooded the engine with fuel, water means you have drowned the bike!. sooty means you have been running rich (potential float issue, or you've been running with the choke on!) , white means you have been running lean, (potential blocked jet issue).

If you don't have a spark, check the wires to the kill/ignition switch, check the ignition switch (old bikes had a tendency to melt the insides of these if the lights were on all the time) spray WD40 in both of these to eliminate water ingress. check the wires to the coil and make sure its all dry and WD40'd. If you still have it connected, check the side stand and clutch switches, its not unheard of that a sticky side stand switch being to blame. Check the CDI and its connectors and wires. wiggle all wires in case one has started breaking down. Again spray everything in WD40. Check all wires are insulated and not frayed and touching the frame or engine. Check fuses are all secure! and not blown.

if none of this works its back to the workshop to test the coil with a multi meter.

Assuming you have a spark,
Before you fit the new plug put you finger over the plug hole and crank the engine. (mind the HT lead or you'll get a belt from it). Can you feel a healthy amount of compression? If there's none then you've either got a valve or valve timing issue or you have a hole in the piston!

Assuming you have compression and a good spark, go back to looking at the fueling.
Remove the carb and carefully remove the float bowl. Is it full of dirt and water? if so clean it and the jets. Just blow through the jets with air at this time (assuming you're still on the side of the road) if your at home use compressed air carefully and a carb cleaning product to blow through all the jets, nozzles passageways etc. (take care not to lose any bits.) remove the float and the float needle and flush this back through to remove any muck from it. Wind the pilot screw in first counting its position (normally between 1 and 2 turns) Then remove it and all its little bits. when you remove this look out for a small washer, spring and o ring. note their position and return them correctly once cleaned.

Once clean, re assemble the carb and refit it to the bike. If its a 2 stroke and you can see in there, check the reeds are all in one piece before you refit the carb.

So now you have good fuel flow, tick,
a clean carb, tick,
a fat blue spark, tick,
Compression, tick.

The bike should now run.

If you suspect an air leak on the inlet rubbers of the carb try spraying WD40 on them as you crank the engine. this will temporarily block any leaks. This will cause starting issues but the bike should still run but with an eratic tick over.

Note as yet we haven't actually changed any parts! Jets don't wear out over the space of a day. if your bikes been getting worse and worse over time then maybe new jets would be prudent to eliminate them from the equation but honestly with proper maintenance and modern fuels, it shouldn't be necessary.

If the bike still isn't playing ball, On 4 strokes, now would be a good time to check the valve timing and do a proper compression test. valve timing is unlikely to have moved, as to do so the cam tensioner would have to fail. if this was to happen then the valves would possibly have hit the piston so you'll be looking at a engine strip down. Time to call the AA to get you home!

On 2 strokes you may have an air leak on the main bearing seals, or any of the carb or inlet seals, or possibly broken reeds.

If your bike wont start after being stood for ages in the garage, the procedure is the same but the cause will probably be a gummed up carb from the evaporated fuel in the float bowl. Wires, switches don't normally break while stood in the garage but that said some may become corroded if you've put it away damp.

When you park your bike up, turn the fuel off and run it until the carb runs dry. (use caution doing this on a 2 stroke!) I let the engine cool a bit then restart it with the fuel off and run it for a minute. My bikes don't normally go more than 2 weeks between rides. This will ensure you always have fresh fuel in the float bowl for starting it next time.

This is meant as a basic guide and to address issues which may cause a bike not to start or run. Its not a definitive guide.

Hopefully this will be some help to someone.
Remember a little knowledge is dangerous. Its easy to cause irreparable damage to an engine fiddling with stuff you don't fully understand.

Author:  Woodywoodster [ Mon Jan 16, 2017 2:21 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips

Good read...had an issue when out this weekend, not resolved yet as I suspect it's the plug..but time will tell..

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Author:  Hugh Cleary [ Mon Jan 16, 2017 3:17 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips


Too cold and wet for my poor old hands out in Derbyshire over last weekend so I decided to replace the headstock bearings and front fork oil of my Serow.

Following on from the lead post I just thought that some of you might like to see the cut outs in the lower headstock section, from above with a long rod you can knock out the lower bearing race.

headstock upper.jpg
headstock upper.jpg [ 623.92 KiB | Viewed 4732 times ]

I have painted a little bit of tippex to highlight the grooves as seen from below.

headstock lower.jpg
headstock lower.jpg [ 785.97 KiB | Viewed 4732 times ]

I bought my Koyo replacements from my local bearing suppliers, Emmett Enterprises of Stockport 0161 477 9020, the upper bearing is SAC264-1 caged ball and the lower roller with integral seal is 32006JRRS. Lots of lovely Silkolene red waterproof grease added.

It is possible to utilise the front axle shaft with suitable large steel flat washers plus 'old' race to act as a bearing installer, smear a little bit of grease in the headstock to ease fitment of the races.



Author:  smokinrider [ Mon Jan 16, 2017 3:45 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips

Is that standard Hugh or something someone has done over the years to get the bearings out?
I'm sure my old DR wheel used to have a groove similar to get the bearing started. once started you could then wiggle the spacer out of the way and work around the bearing to remove it.

The only down side of knocking a bearing from just one side is that it rarely comes out square and in doing so can remove some of the metal from the bearing seat. Likewise bearings should be pressed in rather than beaten in with a hammer. If they start going out of square they will again remove some of the metal from the head stock. Also they are not designed to take the shock forces dealt out with a hammer and drift. They are hardened metal which can and does shatter. (I know ive been there and done it with a stubbon head race before!) Of course a chilled bearing and heated head stock makes life a lot easier and requires less force to install the bearing.

The steel of the head stock isn't a major issue as your head races should last years so you only do the job once or twice in a bikes lifetime, if you keep them greased but for wheel bearings or bikes with ally frames you will soon find that new bearings wont stay in their seats as the removed metal makes them too loose a fit, they then spin on the outer races (wheel bearings especially when they start to sieze) and then its new wheel time.

Author:  Hugh Cleary [ Mon Jan 16, 2017 9:51 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips


The grooves shown in the Serow headstock are pre-machined in the headstock, other marques have similar recesses.

Yamaha, and other manufacturers, do actually recommend removing the bearing seat by impact - but this needs to be done with care so as to alternate from side to side. Heating the headstock using an electric hot air gun aids removal as the headstock will expand ever so slightly, but again care is needed and do not take too long or the bearing seat will heat too :shock:

yamaha hs.jpg
yamaha hs.jpg [ 21.89 KiB | Viewed 4697 times ]

There are various alternative tool options available to remove the races, such as expanding collets and versions that look like a spring loaded feather duster, each method having its inherent costs and degree of difficulty depending upon just how much 'overhang' there is on which to gain grip or impact. Various options are also available to press the new seats into place, in my case I had a pair of large washers of suitable dimensions and the front wheel axle shaft is of adequate length too. A length of 12mm coarse threaded rod could be used as an alternative, plenty of examples on the internet.

You are quite correct that the bearing seats are not designed for impact as they are far too brittle and can shatter. All of these jobs require care or physical damage and or personal injury can occur so wear safety glasses.

If the housing has been damaged in the past it might be possible to use bearing fit adhesive but it depends upon the extent of the damage and use.



Author:  Joel [ Mon Jan 16, 2017 10:38 pm ]
Post subject:  Re: Smokinrider's technical and mechanical tips

Yup, I used some funky green loctite on my Honda wheel bearings,it set like shit to a blanket and saved me a new wheel/hub.

Author:  smokinrider [ Tue Jan 17, 2017 12:12 am ]
Post subject:  Re: Smokinrider's technical and mechanical tips

I see now. On the laptop the pics were so big I only thought the cut out was on one side.

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