Jackshaft Engine max went from 34mph to 25mph? with a jackshaft and tuned pipe

[StrontiumEthics]

I have a jackshaft kit, tuned pipe, and a dax 70cc engine. However today my engine started to act weird. Before it could hit 33-mph fairly easily. Now its struggling to hit 26-mph. What do you think the problem is? Chains adjusted right, bearings are good, just did a tuneup yesterday, and it was ok.

 

[Pablo]

What does your plug look like after a hot, hard run? (and kill and glide)

 

[StrontiumEthics]

It looks dark brown not to dark, more like a tanish dark brown.

 

[Pablo]

Sounds OK. Something basic is not correct. (pardon the brazzilion questions).

What plug, what wire?
Have you widened and matched your intake gasket with manifold and port?
Have you widened and matched your exhaust gasket with header and port?

What is your head torqued to? Any leaks? Checked compression?

 

[StrontiumEthics]

No no its ok, I dont mind the questions. I actually like them.

1. The wire im using is the high performance wire from sickbikeparts, im using NGK B6HS.

2. No I haven't widened and matched my intake gasket with manifold and port. I used the stock intake mani and gasket, and use the copper gasket for my exhaust port.

3. Not to sure what "matched your exhaust gasket with header and port" means.

4. I don't have a torque wrench to torque my heads, but there aren't any leaks as far as I can tell. How can I check Compression?What should the heads be torqued to? Im going to check at my local automotive shop for a torque wrench

Also, I have been hearing a rattling sound but It didn't just happen it was happening for a while now, before I didn't see a decrease in power. Its just one day my top went down from 35-mph to like 26-mph or so. thats what I find very weird. Also I use motor oil for oil in my gas mixture. I recently found out that it really hurt my engine and could be the culprit for the rattling..

 

[Mountainman]

simple compression test may tell a story
all information may be found here in search
MM

 

[Pablo]

Also borrow a compression tester.

Torque should be around 10-12 ft lbs, but go easy if you use those silly stock acorn nuts. It's probably not your porting if you suddenly lost power.

 

[Hawaii_Ed]

My guess would be a leak somewhere. Do you have oil seeping at the base of the cylinder? The base gasket can go, or the head can be loose. I snug my head down every week or so, but I ride pretty hard. I have a bit of mechanical experience, and these engines do not seem to be built to super high tolerances, so I use the German torque spec of gutentight. (good 'n' tight!)

 

[Fabian]

Yes, i agree with Paul - something is clearly wrong with your engine setup.
I have a SickBikeParts Jackshaft kit with a totally stock standard muffler and only a modified intake tube.

My bike easily cruises at 25 miles an hour and has no problems hitting 30 miles an hour with a verly light tail wind.
With the optional 11 tooth Jackshaft sprocket fitted and an 11 tooth smallest gear on the 9 speed cassette, my bike sits on 3500rpm at 30 miles an hour.

You can use ordinary motor oil in your engine but it must be at 16:1 oil/fuel ratio and you must increase the size of your main jet to compensate for the lean air/fuel mixture caused by using so much oil in the fuel.
You must also use the highest (non alcohol fortified) fuel you can get at the petrol pump to compensate for the octane lowering qualities of excessive oil in the 2-stroke mix.

Basically, using ordinary motor oil in a 2-stroke engine at 25:1 or greater is a recepie for engine disaster

Fabian

 

[StrontiumEthics]

You must also use the highest (non alcohol fortified) fuel you can get at the petrol pump to compensate for the octane lowering qualities of excessive oil in the 2-stroke mix. Fabian

What do you mean by this?