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I’ve had this MT-A4 B1 rep for 3 weeks or so now and finally got to take it out last night. Drove out to a go kart track, running late, far away. Didn’t get much time but was a nice little taster. I’m going for a 4 hour session tomorrow.

The bikes looking real good in my opinion. I pushed the coolant reservoir out with a straight bracket and new hoses. This allows me to have the clip ons pretty much straight but still turn lock to lock both sides. A few R6 stickers here and there as I have a red n white R6 aswell for when the weather isn’t so bad lol.

The bike seemed to run well for about 2 laps, I was only on around 3/4 revs as I’ve still got to run in the bike but the powerband was kicking in nice. Then it just kind of started to bog and lose power. I pulled in, she didn’t sound as healthy and kept cutting out. I kept running it on the stand l, fiddling with the idle screw to try and get her nice. I did buy this ram air foam air filter and had laced it with air filter oil (as you do on mx bikes) and thought this is possibly starving the engine of air? So took it off for a minute and the bike seemed to be okay then. Eventually put the filter back on and she ran like a dream again. Got another 10-15 laps in. Still not full revving but the powerband felt good.

So far mod wise I’ve literally just swapped out the stock plug for an ngk b9egv I believe it was, as suggested in the manual. Replaced the tin reed petals for carbon ones and then swapping out the standard filter for that big foam ram air one. I bought a 72 tooth rear sprocket last night aswell after being recommended by one of the lads there. I’m currently waiting on an rpm gauge to set my clutch correctly and also a digital micrometer for setting the squish.

Anybody got any other suggestions for mods for speed, reliability, etc apart from a dellorto carb which is in the pipeline? Just want to make it as good as it can be really. The track I’ve took it to has a proper mini moto shop with all the spares and performance parts btw.

Another quick one aswell. At some point my choke lever stopped locking into place. I haven’t really needed to use it but I remember when I first got the bike, if you put the choke on, it would lock into the down position. You would have to push the lever to the one side for it to spring back up and turn the choke off. Now it won’t stay in the down/on position. It just springs straight back up. Any ideas? Ive tried to look to see how it works but I’m not quite sure.

Thanks everyone for all your information. Hope you like the bike 👍🏻
 

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I’ve had this MT-A4 B1 rep for 3 weeks or so now and finally got to take it out last night. Drove out to a go kart track, running late, far away. Didn’t get much time but was a nice little taster. I’m going for a 4 hour session tomorrow.

The bikes looking real good in my opinion. I pushed the coolant reservoir out with a straight bracket and new hoses. This allows me to have the clip ons pretty much straight but still turn lock to lock both sides. A few R6 stickers here and there as I have a red n white R6 aswell for when the weather isn’t so bad lol.

The bike seemed to run well for about 2 laps, I was only on around 3/4 revs as I’ve still got to run in the bike but the powerband was kicking in nice. Then it just kind of started to bog and lose power. I pulled in, she didn’t sound as healthy and kept cutting out. I kept running it on the stand l, fiddling with the idle screw to try and get her nice. I did buy this ram air foam air filter and had laced it with air filter oil (as you do on mx bikes) and thought this is possibly starving the engine of air? So took it off for a minute and the bike seemed to be okay then. Eventually put the filter back on and she ran like a dream again. Got another 10-15 laps in. Still not full revving but the powerband felt good.

So far mod wise I’ve literally just swapped out the stock plug for an ngk b9egv I believe it was, as suggested in the manual. Replaced the tin reed petals for carbon ones and then swapping out the standard filter for that big foam ram air one. I bought a 72 tooth rear sprocket last night aswell after being recommended by one of the lads there. I’m currently waiting on an rpm gauge to set my clutch correctly and also a digital micrometer for setting the squish.

Anybody got any other suggestions for mods for speed, reliability, etc apart from a dellorto carb which is in the pipeline? Just want to make it as good as it can be really. The track I’ve took it to has a proper mini moto shop with all the spares and performance parts btw.

Another quick one aswell. At some point my choke lever stopped locking into place. I haven’t really needed to use it but I remember when I first got the bike, if you put the choke on, it would lock into the down position. You would have to push the lever to the one side for it to spring back up and turn the choke off. Now it won’t stay in the down/on position. It just springs straight back up. Any ideas? Ive tried to look to see how it works but I’m not quite sure.

Thanks everyone for all your information. Hope you like the bike 👍🏻
On my old Del,Orttos and Del reps the choke automatically springs up or clicks down when you flick the throttle.....

Some carbs you lift the knob and turn it 1/4 turn to lock it then you manually release it by turning it opposite of how you locked it to unlock it.

If its the fold down style you may have lost the lil spring loaded ball bearing that holds it in place...

As far as mods buy a 21mm carb also buy it with a " mainjet assortment pack"...…….

Better reeds are a good upgrade too

Learning the art to properly tensioning the chain is a plus too......

You're already doing the rear sprocket...…It wont give you extra speed;-just quicker acceleration so you can keep the revs up…You'll probably lose 5-8mph on the topend ....

Running it on the recommended 95 octane at 33:1 non-ethanol blended fuel.

Oh and you're not supposed to oil the airfilter...Its not a MX bike..

The oil is used to trap the dirt and on an asphalt track theres only pebbles and rolled-up rubber balls besides the oil naturally appears on the air filter as the engine runs as little spittles of fuel spits back through the air inlet at times when the reeds don't do their job right//...

My Polini doesn't even have an airfilter..It has a tuned air box with five 14mm free flowing holes that are wide open ........……

Works 100% better on wet and damp race tracks and even on hot humid days over the style you have that's for sure...

Oh and on hot humid days you want to run an oxygenated non-ethanol blended fuel to keep the edge...

You should also be more observant of how the faster guys set themselves up and the steps they take to get their race machines ready to rock n roll....It may give you good ideas...….

I used to catch spies of the competition all the time trying to see how my rides are setup and the products I use at the racetracks...

I pull the labels off the spraycans and put the description of what the product is in sharpie marker plus also put some stuff in other brand name containers and ziplock bags to throw them off...….LOL

 

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Discussion Starter #3 (Edited)
On my old Del,Orttos and Del reps the choke automatically springs up or clicks down when you flick the throttle.....

Some carbs you lift the knob and turn it 1/4 turn to lock it then you manually release it by turning it opposite of how you locked it to unlock it.

If its the fold down style you may have lost the lil spring loaded ball bearing that holds it in place...

As far as mods buy a 21mm carb also buy it with a " mainjet assortment pack"...…….

Better reeds are a good upgrade too

Learning the art to properly tensioning the chain is a plus too......

You're already doing the rear sprocket...…It wont give you extra speed;-just quicker acceleration so you can keep the revs up…You'll probably lose 5-8mph on the topend ....

Running it on the recommended 95 octane at 33:1 non-ethanol blended fuel.

Oh and you're not supposed to oil the airfilter...Its not a MX bike..

The oil is used to trap the dirt and on an asphalt track theres only pebbles and rolled-up rubber balls besides the oil naturally appears on the air filter as the engine runs as little spittles of fuel spits back through the air inlet at times when the reeds don't do their job right//...

My Polini doesn't even have an airfilter..It has a tuned air box with five 14mm free flowing holes that are wide open ........……

Works 100% better on wet and damp race tracks and even on hot humid days over the style you have that's for sure...

Oh and on hot humid days you want to run an oxygenated non-ethanol blended fuel to keep the edge...

You should also be more observant of how the faster guys set themselves up and the steps they take to get their race machines ready to rock n roll....It may give you good ideas...….

I used to catch spies of the competition all the time trying to see how my rides are setup and the products I use at the racetracks...

I pull the labels off the spraycans and put the description of what the product is in sharpie marker plus also put some stuff in other brand name containers and ziplock bags to throw them off...….LOL

Thanks for the reply mate. I’ve defo lost something for the choke lever to not lock down any more.
You’re the first I’ve heard about running a 21mm carb. Would really appreciate any links to buy the carb and manifold.
Yeah I thought I might have messed up oiling the filter. You live and learn. I will fit the stock one back for now, wash the new foam one and let it dry. Thanks for the info mate. Have already put carbon reeds in.
I always run shell v power which is about the best fuel you can by in a petrol station Here in the UK if you’re not from here.

Those links would be greatly appreciated though mate.

I seemed to have burned a clutch shoe off in the short time I was on track yesterday. I have replaced it. I’m thinking of buying a decent clutch and clutch bell from the mini moto shop at the track tomorrow.
 

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Hi Tonck,

I have just bought the same bike on ebay for £220, first thing I did was fit a new NGK spark plug and carbon reed petals. After filling up the coolant for the first time, I noticed a small leak coming from the pull start casing, on closer inspection I have found that the leak is coming from the water pump pulley bearing. There are a few posts on here saying the stock Chinese water pump seals are pretty poor, I haven't started the bike yet but wondering if you have had the same issue? I just ordered new bearings, seals and gaskets from Germany and will attempt the fix before firs use.
 

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Hi Tonck,

I have just bought the same bike on ebay for £220, first thing I did was fit a new NGK spark plug and carbon reed petals. After filling up the coolant for the first time, I noticed a small leak coming from the pull start casing, on closer inspection I have found that the leak is coming from the water pump pulley bearing. There are a few posts on here saying the stock Chinese water pump seals are pretty poor, I haven't started the bike yet but wondering if you have had the same issue? I just ordered new bearings, seals and gaskets from Germany and will attempt the fix before firs use.
EPR had the same problem except his whole waterpump was locked-up too and he had to practically rebuild a brand new engine over before it ever had a chance to wear out.......
 

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Mine is the 50cc version, ( 46cc ), I don't think it was new or it sat for along time, from Tsunamibike in Canada which is now gone. Paid $410 USD plus shipping. Never start it with no water inside, your head gaskets is an O ring, of junk China rubber, the crank and 2 small pump shaft bearings w/ China seal. Have to remove the engine and split the cases, to fix it.
Get the numbers off all your bearings, then search for new stuff, I got SKF crank bearings as well as 2 small pump shaft bearings and a Dupont Red Viton silicone seal. Way better than stock, A Polini pump O ring pump drive belt should work, you have to keep an eye on it all the time. You can put a small hole in the front of the pull starter housing so you can see inside.
 

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Nice kit, that should do the job, much easier than finding part by part.
 

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Cheers EPR, the kit I purchased has all the bits you mentioned and I intend on fitting it all. As the case will be already split do you think it's worth while Grinding back the reed stoppers or is it a waste of time?
One worthwhile mod is drilling the oiling hole in the piston that cools the exhaust bridge 1 size larger...….

Another is drilling the hole in the case by the pullstarterto see if the waterpump belt it spinning......
 

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Discussion Starter #11 (Edited)
Hi bro how fast is your motorcycle
I’m still running it in mate so not giving it full throttle. I was quicker than my mates on genuine £1500 air cooled blatas. I had a go and they were little beasts to be fair. But yeah, my bike isn’t far away at all on first impressions.

Hi Tonck,

I have just bought the same bike on ebay for £220, first thing I did was fit a new NGK spark plug and carbon reed petals. After filling up the coolant for the first time, I noticed a small leak coming from the pull start casing, on closer inspection I have found that the leak is coming from the water pump pulley bearing. There are a few posts on here saying the stock Chinese water pump seals are pretty poor, I haven't started the bike yet but wondering if you have had the same issue? I just ordered new bearings, seals and gaskets from Germany and will attempt the fix before firs use.
Alright mate, sorry to hear that. I guess it’s just bad luck with these bikes. It had a good run last night after some clutch problems (Bought one off eBay, ran poor so I ended up putting two worn clutches that come with the bike together to make one) Didn’t seem to have over heating or leaking issues. The very end of the night I noticed the exhaust heating my *** a fair bit so I just gave it a rest.

I’ve read these Chinese water pumps fail regularly so I’m looking into replacing mine for genuine Blata parts fairly soon.

One worthwhile mod is drilling the oiling hole in the piston that cools the exhaust bridge 1 size larger...….

Another is drilling the hole in the case by the pullstarterto see if the waterpump belt it spinning......
Is there a thread on that piston mod you’re talking about? I’m fairly handy but that’s nothing I could go into blind. Also any pics of this water pump viewing hole? I just wouldn’t go drilling any holes into an engine without more research. I defo appreciate the tips and like the idea of being able to check to see if the belt is doing it’s job. Nice one.
 

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Discussion Starter #12 (Edited)
So I had the bike at m4 karting last night and I had the best time going. It was a lot quieter than Friday (About 4 bikes on track at any one time) After Friday’s little run, I inspected the clutch and noticed i had burned a shoe off. I had a spare I had ordered off of eBay which didn’t seem to actually fit when I got it so I got the file out and got it on the bike ready for last night.

Got the bike warm but the powerband just did not seem to kick in at all with me on the bike even though it would do nicely whilst on the stand. In my head I determined that the clutch must have been too small to pull me from the get go. Why did I have to file the center to get it to fit? So I set about putting the two clutches that came with the bike together. I had one good arm/ shoe on one clutch and then the clutch I had on Friday which seemed to work great but had shattered a shoe.

Put those two together and BOOM! The powerband was there straight away. Bike ran great even on 3/4 throttle. Not getting out shone by anything on the track at any one moment.

At some point 2/3rds of the way through the 5-9pm session I actually convinced the souls of my feet to face eachother on the foot pegs and it was non stop knee down action after that. I felt quick and was easily smoking my mates on the rented air cooled blatas. I had an absolute blast with it.

My mates bike unfortunately blew a back tyre on his second lap. Him and another mate rented their bikes and had a great time. I had a 10 minute session on the hire bikes and although they were quick (I was buzzing I was able to keep the bike pinned as much as possible as apposed to riding my own bike) and they was very grippy due to the superior tyres. I didn’t like the size of them. I felt much more unstable on it compared to my bike which seems to be slightly bigger than everything else about.

I have just ordered a genuine blata clutch and will buy some spare arms/shoes when I’m next at the track. Im still waiting on this rpm gauge (trailtech tto) to land. Any step by step threads around for setting the clutch engagement? I feel taking the clutch on and off along with the chain and wheel and all that a bit long and I believe there is a right way of doing things I don’t know about.

Really swaying towards the dellorto 17.5 phva carb aswell. Been eyeing up the bits including the stuffer to go into the reed block. Might not be using the right names there but this is the link. Hope I’m allowed to post the link. If not please remove https://shop.goped-scooter-tuning.de/epages/15355238.mobile/en_US/?ObjectPath=/Shops/15355238/Products/050521 I’ll post a picture with a red ring aroundwhat I believe this part to be on the diagram.


The first picture is of mine and my mates cag which blew the rear tyre after one lap! Gutted is not the word lol!
 

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Discussion Starter #14
CAM2 is talking about make the oil hole over you crank bearings 1 size bigger, then I also taper the top of the hole cause oil will collect there.
Thanks for the pics mate but I’m too much of a newbie to know which is which without a bit more detail for me to understand. Thank you for trying to help though mate.
 

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Discussion Starter #15
CAM2 is talking about make the oil hole over you crank bearings 1 size bigger, then I also taper the top of the hole cause oil will collect there.
After the bike has had a good run I am planning on stripping and rebuilding with all new and better quality seals and gaskets. I will hopefully know enough by then to tackle it. I’m no stranger to getting my hands dirty and done a fair bit of work on bikes but engine internals are new and intimidating to me. No matter how small the engine lol. Will look at the dremel aspect of things whilst I’m rebuilding. Thank you.
 

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You can't see the hole in those photos, see the flat spot where its closest to the bearing and where the cyld fits in, on that shelf is a factory hole that lubes the crank seal and the bearing, I drill it one size bigger and hit the top with a countersink.
 

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Set the springs to 21-22mm length (springs only!) or with the gaug to 8000rpm, that should be a good starting point, engine and clutch should be warm to setup it. You can only do it step by step always 1/4 or 1/2 turn, then ride a turn or two. It is also very important that all three jaws open at the same time.
 

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Discussion Starter #18
You can't see the hole in those photos, see the flat spot where its closest to the bearing and where the cyld fits in, on that shelf is a factory hole that lubes the crank seal and the bearing, I drill it one size bigger and hit the top with a countersink.
So am I right that there would be a hole on both sides where I’ve put the rings? To lube the two sides carrying crank bearing and seals?
 

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Discussion Starter #19
Set the springs to 21-22mm length (springs only!) or with the gaug to 8000rpm, that should be a good starting point, engine and clutch should be warm to setup it. You can only do it step by step always 1/4 or 1/2 turn, then ride a turn or two. It is also very important that all three jaws open at the same time.
How do you ensure all three open at the same time? Just setting each spring exactly with the micro metre or actually matching them in weight aswell? Is it important to set the clutch warm?
 

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You can't see the hole in those photos, see the flat spot where its closest to the bearing and where the cyld fits in, on that shelf is a factory hole that lubes the crank seal and the bearing, I drill it one size bigger and hit the top with a countersink.
Fair play EPR, 👌did you cnc mill that case yourself? Would love to get the 3d model off you if you did...
 
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