Don't have a picture BUT a head spacer would have exactly the same shape as a head gasket - just thicker.
You may be right about the numerical CR calc difference? However, I'd guess that earlier CRs were much lower due to the limitations of air cooling if nothing else. My 250 Ossa MAR was so easy to kick that my 105 lb wife could start it. However it does have a looooong kick start lever.
I don't even actually have the bike yet but have a friend with the same bike that I have kicked a few times.
I can start it but it is sort of marginal and I think it would get very annoying at best on a hot day when I'm tired, etc.
I don't need the power of the 270 so I'm thinking why not detune it and make it easy to kick (or go the 200 route)
Re: The 30% reduction in CR IS a lot but Adrian said it had worked well for several of his customers. I've found a 2008 250 manual that lists the CR at 11:4 to 1 - WOW --- I think the CRs on the early 70s trials bike were around 6:1
THANKS to both of you. I talked to Adrian at Lewisport and learned that he has successfully used as many as 3 of the 1 mm head spacers he had made for some earlier model Gas Gas 2t 250-300 bikes to tame them and make them start easier. 3 mm looks like it would lower the compression ratio on my 270 by about 1/3.
I JUST made a deal to get a one and now I am on a quest to make it easier to kick start. I'm OLD!!!
I had a thread on this on the General board - before I'd settled on a specific bike (and because I have a gal friend with the same issue) but thought you folks on this board might have more good ideas on this specific bike.
I'm thinking of retarding the timing - maybe 5 degrees???
I'm also thinking of adding base gasket(s) to raise the cyl - maybe 1mm to 3mm???
OR I was thinking of making a 2mm to 3mm replica of the head gasket out of aluminum as another way of increasing the combustion chamber volume without changing port timing???
Do you know anything about how difficult this would be to make?
Also would I want to used a standard head gasket on BOTH sides if it?
I guess I could also grind some metal out of the dome part of the cylinder head which would avoid messing up the squish area around the edges and not affect the port timing - but of course this is not reversible.
Although getting it to tuck in might be a problem - the idea of lengthening the kick starter seems like it would help too? Anyone know of a source for a broken on I could get to try it on?
In my search for easy starting 2t trials bikes some have suggested motor mods to ease kick starting.
The items that have come up so far are lowering compression and/or adding a compression release for starting (like was used in the 70s as a brake assist) by adding another hole (like a spark plug hole) in the head? Is this even possible with water cooled motors?
Does anyone have any knowledge or experience with these mods? OR any other ideas?
I'm interested in anything but wondered about the "optimum" compression ratio to get a good balance between starting ease and maintain sufficient power? And/or ideas on how low one can go without really messing up the motor performance?
Also pros and cons of just adding to base gasket thickness VS removing metal from the dome of the combustion chamber in the head (to avoid messing up the "squish" area around the perimeter of the pistion/head?
Also does anybody know of a trials bike that one could add an e-start from a related enduro motor to?
Well I just got the top part of the cylinder head off and found what at least some of the problem is. The fiber cam chain guides are destroyed and the red stuff is all over inside the top head, etc. Thus the cam chain is very loose and the cam can be rotated quite a bit with the crank stopped.
SO now I'd appreciate any help you can offer on what parts I will need to fix this (besides the obvious cam chain guides). Also will I be able to insert the new cam chain guides without removing the cylinder head and/or cylinder, etc.? Is there a way to determine if the cam chain and gears are OK? The cam chain can not be significantly pulled away from the cam gear at 12:00 o'clock if the chain is held against the gear at 3:00 and 9:00 o'clock - so my initial assumption is it is OK.
Right now the engine is still in the frame (but dropped down a little to get the cam cover off) with all the wires and carb, etc. attached and with the swing arm bolt still installed. Will I need to remove it? OR can I get the side cover/case off and the new cam guides installed with the engine still in place?
Well I tired the really easy fix of just doing the cam chain tensioner check but no luck there.
I now have the decompression spring, etc. so will tackle that next.
I'm a little confused by your statement about setting the TDC per the service manual? The valve gear section 4.17.2 tells one to:
Take care to time up the camshaft properly. The
crankshaft is locked at TDC by the special bolt which
was fitted earlier (see 4.11). Position the camshaft
so that the timing mark (A) is horizontal on the
exhaust valve side.
When I go to section 4.11 it show a bolt going into the gear box area from the front of the engine and says:
Lock the crankshaft at TDC using the appropriate
bolt (7),
However it never says anything about removing the bolt and the parts manual show the bolt as a standard part?
Are you telling me I need to do this locking of the crankshaft? And IF SO am I supposed to get a LONGER bolt to do the locking and then put the standard bolt that I removed back in afterwards so the crank is no longer locked?
OR are you just telling me to line the cam gear mark up with the front of the head and mark the chain then hold it up and get it back onto the cam gear in the same place?
Sorry for all the questions - but I really appreciate your help!!! It also looks like you are telling me I don't need to remove the engine (but rather can just drop the front down)! YEA!
Thanks for all the replies! It seems that most are recommending the smaller displacement 2ts and that may indeed be my best bet.
However, I was wondering if there are any particular brand or model ~ 250cc 2ts that are generally easier to kick than others due to things like lever length, placement, gear reduction, etc? Also how about things like a compression release (like I had many years ago on my 1970s 2ts (when they didn't have good waterproof brakes)?
I am interested in getting a used modern trials bike but am concerned that some of them may not be easy for an OLD guy like me to start - particularly when I'm tired and the bike has been dropped, etc. I have e-start on my trail and enduro bikes for this reason.
I recently saw a 2008 Beta 270 Rev 3 for sale that sounded reasonable. I asked a friend that has a bike like that about it and he told me it is rather difficult to kick start - short kick lever requiring lots of force to spin the motor.
So my question is what brands and models of used trials bikes are the EASIEST to start, hot or cold?
My preference is for a 2 stroke due to the lighter weight, etc. but would consider a 4 stroke if there are no easy starting 2 strokes.
jimg - Thanks for the reply. I will do as you suggest before going after the spring replacement. Maybe I'll be really lucky?
The only reason I didn't jump on it the first time is that I ASSUMED that since my noise was loud and sudden that it was more likely the spring. BUT your idea is certainly worth a shot and basically free!
WOW! I'm impressed by the responses! Thanks Folks! I got sidetracked for a few days with a problem with another bike but now I'm gonna try the Beta.
Hopefully my problem is the spring for the decompressor weight. The noise appeared suddenly and sounds BAD. I had to ride the bike for a mile or so with the noise and tried not to rev it too much.
From looking at the manual - I THINK I can replace the spring without getting into the bottom of the engine? Is it possible to get the cam out and back in without messing with the water pump or even removing the bottom part of the cylinder head? It seems like I MIGHT be able to just take the top of the cylinder head off then slip the bearings off the cam then get the cam out to replace the decompressor spring. If I marked where the cam sprocket teeth mate to chain, MAYBE I could reassemble it back the same way to avoid having to do the locking of the crank at TDC routine?
IF this plan is workable and it is the spring - I don't see any parts other than the spring that I'd need - unless it is likely that the weight is damaged? This assumes I could reuse the O-rings that are on the little covers one uses to check and adjust the valves, etc. I'd appreciate any guidance you can offer. I'm not too cheap to by any parts you think I'll need. Just trying to keep it as simple as possible. I'm reasonably competent at this kind of stuff BUT sure don't want to get into it any deeper than necessary.
My 2009 300 4t sounds BAD. I haven't done any investigation yet to determine what is wrong but it is making knocking sounds so probably NOT trivial.
Does anyone have recommendations on repair service available locally OR that I could ship the motor to (assuming it is a serious problem)? I live in Frederick Maryland.
There is a local dealer but he has never been inside one of these 4t engines.
09 Beta Evo 300 4t with EXTENSIVE mods (see below) to make it an ultimate OLD guy trail bike.
The 300 4t is AMAZING and great for riding the really gnarly stuff AND should be good for me when I get too OLD and fat (I'm only 69 and 200 lbs. now) to ride my KTM in the dirt. Believe it or not, it is actually quite comfy to ride even sitting on the seat as long as you are not going really fast over rocks/logs, etc.
Long Ride Kit (1.1 Gallon Aux Tank & Seat)
Scotts Stabilizer
BBR Seat at Normal Trail Ride Height
16" Rear Wheel (More Rake & Trail & Lower Pegs)
Full Knobys 21" Front & 16" Rear
6" Rise Jitsie Handlebars
Thicker Fork Oil in Right Fork ONLY for Increased Dampening
Significantly Stiffer Front and Rear Spring
Max Damping on Rear Shock
Lowered Shifter
Acerbis Rally Pro X Rally all plastic Handguards
Tool Bag Under Seat
Garmin eTrex GPS on Handelbar
This FrankenBeta is terrific. I've now made the following ADDITIONAL mods and the bike is even better.
Substituted Garmin Montana for the eTrex
Added an EFM Auto Clutch
This is a great improvement for me (because all my other bikes have auto-clutch and I was having trouble rememberiring to use the Beta clutch.
ALSO the makes the gap between 3rd and 4th a non problem as, within reason, you can use 4th at very low speeds
Added a Left Hand Rear Brake (which is in addition to the normal foot brake)
This provides great flexibility and works well when riding sitting down (where it is hard to use the foot brake)
Added SPIKED knobby tires for use in winter on ice, snow and wet roots and logs.
Tried them out about 10 days ago and was AMAZED at the traction. I was never even able to use their full potential becasue I didn't have the confidence to reley on them. You can hit a slick log at 60 degrees and it just goes right over - no drama.
I'm NOT much of a trials rider buy have done quite a bit of experimentation in the process of modifying my 2009 4t suspension for trail riding.
My advice would be: Get stiffer springs (by the way increaseing Pre-Load does NOT make a spring stiffer just sets the ride height up higher).
Increase the damping on the rear shock to damp the rebound of the stiffer spring (there is quite a bit of range available). Incresed the viscosity of the oil in the right fork only. This will increase compression damping and provide an increased range of rebound damping to control the stiffer springs.
Help! Can Get The Fix Valve Chain Guide Into My 4T
in Beta
Posted · Edited by bigbird2
deleted