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Motorized Bicycle Trouble Shooting Use this area to post problems that may arise, if you could use some help in figuring out what is wrong with your engine and what needs to be done to achieve top performance.

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  #21  
Old 04-29-2013, 02:32 AM
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Tyler6357 Tyler6357 is offline
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Default Re: So your HT won't start, well let's take a look

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Originally Posted by AzRigidRider View Post
Hmm good call Tyler, I haven't replaced head gasket but did get a bottom gasket along with jug and piston with upper needle bearing and wrist pin. As far as spark haven't been about to confirm sparking I will have to take an ohm reader to magnito and ignition. I've got a NGK bp7hs that isn't even a month old with minimal carbon build up but guess there's a chance of it being foul if ohms check out. And for carb, is there any specific methods for checking good flow?
Well, when stuck, go back to basics. To get it to start you must have 3 things, fuel, spark, and compression. Since you just replaced the cylinder and piston, it leads me to suspect a problem with compression. You might have an air leak somewhere. First, the head gasket should be replaced because it must conform to the piston to make a good seal and what works with the old piston doesn't always seal correctly with a new one. Second, also make sure that the head is sitting flat against the top of the tub and is torqued down enough to seal the head. Third, make certain that the cylinder is sitting all the way down and flat against the gasket for the bottom end. Four, you might consider removing the cylinder and make certain that the piston rings are sitting in correctly. They should be lined up and pinch together against the grooves on the piston as you slide the cylinder over the piston, it can be kinda tricky. Another common place for air leaks is at the intake manifold both at the engine intake and where the carb connects to it, usually you will see small leaks of oil and gas if you have a leak here. It's best to test the spark with an ohm meter but you can check if you are getting a spark at all by turning off the lights and checking it in the dark so you can see the spark. As far as the carb, take it apart and clean it, make certain that the jet is not clogged and is securely screwed in, make sure that the float is filling with gas and isn't leaking. Sometimes just taking things apart and putting them back together can solve a problem even if you never find out exactly what it was, Also, anytime you replace the piston and or rings you should mix your gas with more oil and follow break in procedures again. Part of breaking an engine in is getting the piston rings to set properly so take it easy on the throttle for the first few tanks of gas.
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  #22  
Old 04-30-2013, 10:51 PM
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Question Re: So your HT won't start, well let's take a look

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Originally Posted by Tyler6357 View Post
Well, when stuck, go back to basics. To get it to start you must have 3 things, fuel, spark, and compression. Since you just replaced the cylinder and piston, it leads me to suspect a problem with compression. You might have an air leak somewhere. First, the head gasket should be replaced because it must conform to the piston to make a good seal and what works with the old piston doesn't always seal correctly with a new one. Second, also make sure that the head is sitting flat against the top of the tub and is torqued down enough to seal the head. Third, make certain that the cylinder is sitting all the way down and flat against the gasket for the bottom end. Four, you might consider removing the cylinder and make certain that the piston rings are sitting in correctly. They should be lined up and pinch together against the grooves on the piston as you slide the cylinder over the piston, it can be kinda tricky. Another common place for air leaks is at the intake manifold both at the engine intake and where the carb connects to it, usually you will see small leaks of oil and gas if you have a leak here. It's best to test the spark with an ohm meter but you can check if you are getting a spark at all by turning off the lights and checking it in the dark so you can see the spark. As far as the carb, take it apart and clean it, make certain that the jet is not clogged and is securely screwed in, make sure that the float is filling with gas and isn't leaking. Sometimes just taking things apart and putting them back together can solve a problem even if you never find out exactly what it was, Also, anytime you replace the piston and or rings you should mix your gas with more oil and follow break in procedures again. Part of breaking an engine in is getting the piston rings to set properly so take it easy on the throttle for the first few tanks of gas.
Right on man, that all makes sense. So i checked the 3 basics and came up with this... Carb seems good with no leaks. I took an ohm meter to the wire connections which said has power but no spark and has good plug gap an everything. Whats crazy is I took head off to check seals (do need new head gasket) and found that the piston is surpassing the jug when rod pushes piston in full upqright position hitting head which is kinda scoring the rim edge on head, very unusual since I got cut on piston and jakes jug specifically for the 66cc. I've got no clue why it'd be doing that.
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  #23  
Old 05-01-2013, 04:06 AM
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Default Re: So your HT won't start, well let's take a look

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Originally Posted by AzRigidRider View Post
Right on man, that all makes sense. So i checked the 3 basics and came up with this... Carb seems good with no leaks. I took an ohm meter to the wire connections which said has power but no spark and has good plug gap an everything. Whats crazy is I took head off to check seals (do need new head gasket) and found that the piston is surpassing the jug when rod pushes piston in full upqright position hitting head which is kinda scoring the rim edge on head, very unusual since I got cut on piston and jakes jug specifically for the 66cc. I've got no clue why it'd be doing that.
If the piston is hitting the head that is a problem. The aluminum piston won't last long if it is hitting the steel head. I doubt it could seal properly under those conditions. I'm not certain exactly what kind of engine you have. I was looking at Dax and I noticed that they have 2 different styles of 66/cc engines, a type D and a type J (check page 3 of the parts page rows 9 and 10). Type J has a 5mm longer Con Rod than Type D. I don't know if the cylinders for each are interchangeable or not or how much a difference just 5mm can make. Does the new jug you got match the old one in height and bore size? I don't know if you could try putting a 2nd gasket on the bottom of the cylinder and solve it or it could be that you need a longer cylinder. Compare the new and old pistons, are they the same? Also, I don't know what kind of head your engine has? Is it a slant head? It could be that you can get a different kind of head to solve it. I'm pretty sure the pistons of the Type's D & J are interchangeable. However, I'm not an expert on these engines and I'm still learning myself. I'm sorry but I can't say that I'm 100% sure what to do but if the piston is hitting the head I'm quite sure that is the main reason why it won't start. Also, if you are getting power and no spark try a different spark plug.

Last edited by Tyler6357; 05-01-2013 at 05:33 AM.
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  #24  
Old 05-01-2013, 10:54 AM
crassius crassius is offline
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Default Re: So your HT won't start, well let's take a look

yep, you need to measure quite a bit before ordering - some rods are diff length, some barrels are diff height, some pistons have diff wrist pin locations

pistons & barrels have diff diameters, but if bought as a set ,usually match

in cases where the fit is close to right, a thick extra gasket or two can fix it, but a measurement is needed to determine how the port timing will come out if the gasket is added to base of barrel or under the head

it's getting REAL hard to mix parts on these things
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  #25  
Old 05-01-2013, 08:20 PM
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Post Re: So your HT won't start, well let's take a look

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Originally Posted by Tyler6357 View Post
If the piston is hitting the head that is a problem. The aluminum piston won't last long if it is hitting the steel head. I doubt it could seal properly under those conditions. I'm not certain exactly what kind of engine you have. I was looking at Dax and I noticed that they have 2 different styles of 66/cc engines, a type D and a type J (check page 3 of the parts page rows 9 and 10). Type J has a 5mm longer Con Rod than Type D. I don't know if the cylinders for each are interchangeable or not or how much a difference just 5mm can make. Does the new jug you got match the old one in height and bore size? I don't know if you could try putting a 2nd gasket on the bottom of the cylinder and solve it or it could be that you need a longer cylinder. Compare the new and old pistons, are they the same? Also, I don't know what kind of head your engine has? Is it a slant head? It could be that you can get a different kind of head to solve it. I'm pretty sure the pistons of the Type's D & J are interchangeable. However, I'm not an expert on these engines and I'm still learning myself. I'm sorry but I can't say that I'm 100% sure what to do but if the piston is hitting the head I'm quite sure that is the main reason why it won't start. Also, if you are getting power and no spark try a different spark plug.
I believe I have the type D head so doesn't have slant. And planing on ordering new head http://www.jnmotorsbikes.com/Product...M1250&CartID=3 but dont know if it will solve the issue. Well my friend you ARE 100% right haha so is Crassius. I took a digital caliper to the new and old pistons to compare specs and dimensions... From top of wrist pin hole to top of piston, heres what i got.. Old one is at about 0.645 and the new is at about 0.845. So a pretty significant difference as far as the pistons go. While the jugs ports are at different depths. I don't know how to determine the length of my con rod without opening crankcase which hopefully is avoidable. I think the jugs heights are just barely off and think the 2nd gasket would correct the jug size issue but not the piston size issue..
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  #26  
Old 05-02-2013, 06:12 AM
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Tyler6357 Tyler6357 is offline
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Default Re: So your HT won't start, well let's take a look

You don't need to open the crankshaft, I'm certain you don't need to crack it. The problem is in the top end. It sounds like the piston and cylinder that you got are not really designed for the type D if they are different from your original ones. You can try to send them back or make them work. You might try using your original cylinder if it's not too thrashed or maybe try 2 cylinder base gaskets. The head might solve the problem. That is a very nice head. I assume it requires the normal head gasket. I recommend that you get a new one. Also, I notice it says:

Quote:
"Please be aware that in order gain the maximum benefit from this cylinder head, you will need to bring the outer edge of the piston to (or close to) the top of the cylinder.*The GT-5 engine has a different crankshaft assembly and piston than most other engines, and has low compression. Adjusting the compression by decking the cylinder jug is necessary for the GT-5 engine in order to gain proper compression ratio."
If you go with 2 cylinder base gaskets you should have no trouble benefiting from this upgrade. I don't think you have a GT-5 engine. You could try it with the new head, head gasket, and 2 cylinder base gaskets and see if solves the problem. If it doesn't I would try a piston closer in specs of your original one. If you do get it going please let us know what you think of the performance of that head. It should give you are performance upgrade and provide better engine cooling too. I have a type D with a slant head. I've done a few upgrades on my bike but so far, the expansion chamber exhaust pipe has been the best one.

Last edited by Tyler6357; 05-02-2013 at 04:59 PM.
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  #27  
Old 05-03-2013, 12:39 AM
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AzRigidRider AzRigidRider is offline
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Default Re: So your HT won't start, well let's take a look

Quote:
Originally Posted by Tyler6357 View Post
You don't need to open the crankshaft, I'm certain you don't need to crack it. The problem is in the top end. It sounds like the piston and cylinder that you got are not really designed for the type D if they are different from your original ones. You can try to send them back or make them work. You might try using your original cylinder if it's not too thrashed or maybe try 2 cylinder base gaskets. The head might solve the problem. That is a very nice head. I assume it requires the normal head gasket. I recommend that you get a new one. Also, I notice it says:
This

If you go with 2 cylinder base gaskets you should have no trouble benefiting from this upgrade. I don't think you have a GT-5 engine. You could try it with the new head, head gasket, and 2 cylinder base gaskets and see if solves the problem. If it doesn't I would try a piston closer in specs of your original one. If you do get it going please let us know what you think of the performance of that head. It should give you are performance upgrade and provide better engine cooling too. I have a type D with a slant head. I've done a few upgrades on my bike but so far, the expansion chamber exhaust pipe has been the best one.
For sure man you got it. The info you've given me and helped me with this is f****** awesome and can't appreciate it enough. I got ahold of jake from jakebike.com and this is what was said.. (Read from bottom to top).

"Wrong piston type. You have a Grube gt5 if that's happening. Copy my cuts on your old piston and use it instead. The Grube has a longer crank and shorter piston, so that happens. There are two piston types. You need type 2. NOT TYPE 5. You will be ahead of the game if you order a very high compression head, use my jug, and your cut on piston. Or I can swap you out a piston. The port timing of that setup will make a good boom and you'll haul ass. But not without adding a high compression head to compensate for the higher sleeve and short piston.

Basically, you have the dream combo just use a #2 piston. ..

Sent with the best of intentions, from Jake

On May 1, 2013, at 10:57 PM, Alex Cohen <alex.cohen11@yahoo.com> wrote:

I just installed both the cut on piston and your jake jug you sell for 66cc motors on my regular stock 66cc and found that the piston is surpassing the jug when rod pushes piston in full upright position hitting head. Can you please give me some insight as to why this is happening..



On May 1, 2013, at 8:21 PM, jake busey <jake@jakebike.com> wrote:

any 66cc
On May 1, 2013, at 9:31 PM, Alex Cohen wrote:

What 66cc motor is required or compatible for your "cut on piston and jake jug"
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  #28  
Old 05-03-2013, 01:39 AM
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Tyler6357 Tyler6357 is offline
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Default Re: So your HT won't start, well let's take a look

@AzRigidRider

Ha, ha, it sounds like he is trying to sell you that head. It's a high quality head but you really don't need it to get the thing to start again. If he offered to switch out the piston for you then I would go for that. If you do that and replace the head gasket you probably could get it to start again. Remember that you can always get the head after you get it running with your old one, but if you got the money for it, hey, go for it, it looks nice!
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  #29  
Old 05-03-2013, 05:07 AM
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Default Re: So your HT won't start, well let's take a look

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Originally Posted by Tyler6357 View Post
@AzRigidRider

Ha, ha, it sounds like he is trying to sell you that head. It's a high quality head but you really don't need it to get the thing to start again. If he offered to switch out the piston for you then I would go for that. If you do that and replace the head gasket you probably could get it to start again. Remember that you can always get the head after you get it running with your old one, but if you got the money for it, hey, go for it, it looks nice!
Yeah true, what a salesmen! Hahah I getcha about the head I was looking to put a better quality head on it prior to all this happening so I might just put it on to get it out of the way haha but not from him I doubt he'll even take the cut on back to swap it due to it getting a notch on each side of piston due to it hitting head while trying to start it before I realized what was happening (attached pic). So I'll probably just get the head, a head gasket, plug and piston all together. Ohh and found this earlier too.. Idk if I'd benefit from this piston in regards to starting it or if I'd just be in the same boat I'm in now as far as piston issue goes.. Guess I could just ask for specs..
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  #30  
Old 05-03-2013, 05:10 AM
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Default Re: So your HT won't start, well let's take a look

Oops forgot to add link for other piston I found which I was referring to at the end of reply ha..

http://www.ebay.com/itm/66cc-Bicycle...7&cmd=ViewItem
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