Lost top speed

[nelsonk1969]

I am guessing all is well with your bike now?
if you snapped a bolt make sure the new one you installed along with the other mounting bolts are the correct case hardened bolts for the application.
many kits will supply the wrong type bolts then provide no warranty. they buy these bolts in bulk and case hardened are much more expensive and take away from the little profit that they do get.

 

[KCvale]

Broke a darn bolt on the rear mount, no wonder.
Here I was chasing problems and it was right there.

Absolute RULE #1 for these 2-stroke bikes operation:

THE ENGINE MUST BE MOUNTED SOLID!​

Simple actually.
Hold your top bar with one hand, your cold engine head with the other, and push as hard as you can back and forth on the engine.
If it moves AT ALL it is a fail and always will be.

Good motor mounts are a berry berry good thing ;-}

 

[Rudz]

Going to get there bolt out in bit, just woke up, worked last night.

I used upgraded stainless socket bolts, must have loosened up on me. They were snug last time I checked. Fml.

I know better than loosely mounting my motor, and no rubber mounts either, I promise.

 

[nelsonk1969]

Stainless steel bolts are not an upgrade unfortunately while they will never rust they can break much easier than a case hardened bolt.
The real downside is if it does break it will be a real mother f r if you need to drill it out.

 

[Dan]

Absolute RULE #1 for these 2-stroke bikes operation:

THE ENGINE MUST BE MOUNTED SOLID!​

Simple actually.
Hold your top bar with one hand, your cold engine head with the other, and push as hard as you can back and forth on the engine.
If it moves AT ALL it is a fail and always will be.

Good motor mounts are a berry berry good thing ;-}

Gonna have to beg to differ just a wee bit. Pushing it hard as you can is not a good thing, IMVHO. Better to check for wiggle. Not at all meaning to be adverserial and you are right, KC. Tight is right. Just saying to much force could be bad, is all.

Stainless steel bolts are not an upgrade unfortunately while they will never rust they can break much easier than a case hardened bolt.
The real downside is if it does break it will be a real mother f r if you need to drill it out.

Great point Nelsonk. Stainless is awesome but brittle and not the best choice when exposed to the vibrations and shear load.

I don't know if this is the best choice but I use automotive studs. If, (and I rarely do) I replace engine mount studs. They hold up great, are cheap and kinda gritty and seem to loosen less.

Not in anyway advice. Just what I do.

 

[Rudz]

I'll look into hardened bolts, thanks.

 

[Rudz]

Put her all back together. I opened the exhaust and manifold, and matched the gaskets. I didn't touch the jug though. The jug is another project.

She runs like a bat out of ****, I left the carb needle on the richest setting, I'll probably play with it later.

Easily hit 30 on an semi flat stretch, I'm happy again.

Looked for hardened bolts on eBay, but they were scarce of metrics. I found some at boltdepot.Com, I think I'm going to order grade 8 zinc plated bolts

 

[Slogger]

http://www.ebay.com/itm/321308613775

I bought these for mine- check the sellers store, he has some stuff you can't easily find. Good Luck!

 

[Dan]

Hardware stores also have them.

 

[nelsonk1969]

Put her all back together. I opened the exhaust and manifold, and matched the gaskets. I didn't touch the jug though. The jug is another project.

She runs like a bat out of ****, I left the carb needle on the richest setting, I'll probably play with it later.

Easily hit 30 on an semi flat stretch, I'm happy again.

Looked for hardened bolts on eBay, but they were scarce of metrics. I found some at boltdepot.Com, I think I'm going to order grade 8 zinc plated bolts

I am glad you figured it out.
At my age I am sure I forgot more than I know about Case hardened bolts
before you go with the grade 8 bolts spend a little time researching the different grade bolts and what applications they are used for.
While grade 8 may be the strongest I don't remember if it is the best choice for the application. It may be I just do not remember. with hardened fasteners
if I remember correctly going too high of a grade can fail just as fast as a non hardened bolt under the right conditions.

when I get time I will look it up online unless you or someone else beat me to it.

 

[Rudz]

Let me know which ones are the best to use

 

[KCvale]

Gonna have to beg to differ just a wee bit.
Pushing it hard as you can is not a good thing, IMVHO.
Better to check for wiggle.
Not at all meaning to be adverserial and you are right, KC.
Tight is right. Just saying to much force could be bad, is all.

(smiles) Agreed, but by pushing the engine back and forth as hard as you can I mean as hard as I can push it with my two arms.

A strong man with both arms and a leg could bust an engine out of one these bikes but if it's mounted right and solid he'd be tired when he was done hehehe.

First you don't need to use studs, I find bolts work better and my local Ace hardware stocks them for cheap.

You can tell a case hardened bolt by the lines or numbers on the top of the hex head.
The more lines or higher the number the harder and stronger the bolt.

We just had to do an easy-out re-bolt and grabbed some 8.8's at Ace for like 20 cents each.

There is little you can do for the back mount but keep it flush against the seat tube but that's all it needs.

A really great front mount makes a world of difference for the lateral movement however and how you keep the back from having to deal with it.
Nothing short of welded mounts works as well as a muffler clamp and plate front mount that I have ever seen.

The muffler clamp gives you a round to flat full grip platform that won't twist, from there it is just spacers and connection plate.

All I know is with 50 or so 2-stroke builds using that method they do the job best and though we might not be able to rip a phone book in half we are not weak, and it's not right until we can't make the engines move when done right and our hands down test.

 

[BarelyAWake]

A really great front mount makes a world of difference for the lateral movement however and how you keep the back from having to deal with it.
Nothing short of welded mounts works as well as a muffler clamp and plate front mount that I have ever seen.

The muffler clamp gives you a round to flat full grip platform that won't twist, from there it is just spacers and connection plate...

...except given the force sometimes needed to secure the clamp mount fully can inadvertently crimp the down tube, as they're intended to do with exhaust systems to form a good fit. It's particularly problematic with aluminum and/or shift kit builds (relocate to tension, repeat) as this can lead to long-term wear & damage.

It is however such a simple modification to address this I'm a bit disappointed that all the assorted merchants offering such muffler clamp mounts still don't offer or mention it, as otherwise the clamps really are one of the better, easy & cheap solutions.

No welding, although a coupla tacks are handy... jus' need to get your own clamp one size over & some pipe (any hardware store) that's "close enough" as you can bend to fit if needful;

 

[maniac57]

...except given the force sometimes needed to secure the clamp mount fully can inadvertently crimp the down tube, as they're intended to do with exhaust systems to form a good fit. It's particularly problematic with aluminum and/or shift kit builds (relocate to tension, repeat) as this can lead to long-term wear & damage.

It is however such a simple modification to address this I'm a bit disappointed that all the assorted merchants offering such muffler clamp mounts still don't offer or mention it, as otherwise the clamps really are one of the better, easy & cheap solutions.

No welding, although a coupla tacks are handy... jus' need to get your own clamp one size over & some pipe (any hardware store) that's "close enough" as you can bend to fit if needful;

Could not have said it better myself. I do this with all muffler
clamp mounts

 

[Goat Herder]

Could not agree more. I was always disapointed to to see any impression from such a clamp.

 

[Rudz]

I use a muffler clamp, wish I could do what "barely" suggested, bet my downtube is so wide that the extra wide clamp barely fits.

So im careful not a torque down with my excessively massive arms

 

[Slogger]

I use a muffler clamp, wish I could do what "barely" suggested, bet my downtube is so wide that the extra wide clamp barely fits.

So im careful not a torque down with my excessively massive arms

Lol!
On my bike the U bolt JUST fit the frame tube.. What to do?
I gave up and plastidipped the ubolt, then bolted it up just tight enough to be snug against the tube, loctited the nuts and put jam nuts behind them to keep it from loosening. There is almost no crushing force on it, and the thing is rock solid.
Plasti-dip was also used on the underside of the gas tank, in the tunnel and out to the mounting studs. The tank is real stable and doesn't want to rotate on the tube or vibrate around. Also did the rear chain stay where the tensioner is mounted, and the tensioner bracket also. So far so good.
The rubbery coating is only a few thousandths thick, but does the job.

 

[KCvale]

(smiles)
There are many ways to mount the front secure, the point is to simply 'make it so'.

 

[Rudz]

I do have a fresh can of plastidip too..... Lmfao project time!

 

[Slogger]

(smiles)
There are many ways to mount the front secure, the point is to simply 'make it so'.

I cheated and got the SBP front mount. They even contacted me and asked for a measurement of the front tube. The one they sent fit perfect.
I read about the split pipe deal after ordering, or I could have gotten one size bigger and mounted it that way. Hopefully it won't crack since it isn't really tightened down hard on the tube. It is definitely immobilized, though. It doesn't budge at all.